Initially required due to the split codepath with how the initial main
process instance was initialized. We used to initialize the process
like:

Init() {
    main_process = Process::Create(...);
    kernel.MakeCurrentProcess(main_process.get());
}

Load() {
    const auto load_result = loader.Load(*kernel.GetCurrentProcess());
    if (load_result != Loader::ResultStatus::Success) {
        // Handle error here.
    }
    ...
}

which presented a problem.

Setting a created process as the main process would set the page table
for that process as the main page table. This is fine... until we get to
the part that the page table can have its size changed in the Load()
function via NPDM metadata, which can dictate either a 32-bit, 36-bit,
or 39-bit usable address space.

Now that we have full control over the process' creation in load, we can
simply set the initial process as the main process after all the loading
is done, reflecting the potential page table changes without any
special-casing behavior.

We can also remove the cache flushing within LoadModule(), as execution
wouldn't have even begun yet during all usages of this function, now
that we have the initialization order cleaned up.

Now that we have dependencies on the initialization order, we can move
the creation of the main process to a more sensible area: where we
actually load in the executable data.

This allows localizing the creation and loading of the process in one
location, making the initialization of the process much nicer to trace.

Like with CPU emulation, we generally don't want to fire off the threads
immediately after the relevant classes are initialized, we want to do
this after all necessary data is done loading first.

This splits the thread creation into its own interface member function
to allow controlling when these threads in particular get created.

Our initialization process is a little wonky than one would expect when
it comes to code flow. We initialize the CPU last, as opposed to
hardware, where the CPU obviously needs to be first, otherwise nothing
else would work, and we have code that adds checks to get around this.

For example, in the page table setting code, we check to see if the
system is turned on before we even notify the CPU instances of a page
table switch. This results in dead code (at the moment), because the
only time a page table switch will occur is when the system is *not*
running, preventing the emulated CPU instances from being notified of a
page table switch in a convenient manner (technically the code path
could be taken, but we don't emulate the process creation svc handlers
yet).

This moves the threads creation into its own member function of the core
manager and restores a little order (and predictability) to our
initialization process.

Previously, in the multi-threaded cases, we'd kick off several threads
before even the main kernel process was created and ready to execute (gross!).
Now the initialization process is like so:

Initialization:
  1. Timers

  2. CPU

  3. Kernel

  4. Filesystem stuff (kind of gross, but can be amended trivially)

  5. Applet stuff (ditto in terms of being kind of gross)

  6. Main process (will be moved into the loading step in a following
                   change)

  7. Telemetry (this should be initialized last in the future).

  8. Services (4 and 5 should ideally be alongside this).

  9. GDB (gross. Uses namespace scope state. Needs to be refactored into a
          class or booted altogether).

  10. Renderer

  11. GPU (will also have its threads created in a separate step in a
           following change).

Which... isn't *ideal* per-se, however getting rid of the wonky
intertwining of CPU state initialization out of this mix gets rid of
most of the footguns when it comes to our initialization process.

Some objects declare their handle type as const, while others declare it
as constexpr. This makes the const ones constexpr for consistency, and
prevent unexpected compilation errors if these happen to be attempted to be
used within a constexpr context.

sirit is a runtime assembler for SPIR-V

These are holdovers from Citra.

We need to ensure dynarmic gets a valid pointer if the page table is
resized (the relevant pointers would be invalidated in this scenario).

In this scenario, the page table can be resized depending on what kind
of address space is specified within the NPDM metadata (if it's
present).

In our error console, when loading a game, the strings:

QString::arg: Argument missing: "Loading...", 0
QString::arg: Argument missing: "Launching...", 0

would occasionally pop up when the loading screen was running. This was
due to the strings being assumed to have formatting indicators in them,
however only two out of the four strings actually have them.

This only applies the arguments to the strings that have formatting
specifiers provided, which avoids these warnings from occurring.

This commit makes sure GL reads on the correct pack size for the
respective texture buffer.

Adjusts the interface of the wrappers to take a system reference, which
allows accessing a system instance without using the global accessors.

This also allows getting rid of all global accessors within the
supervisor call handling code. While this does make the wrappers
themselves slightly more noisy, this will be further cleaned up in a
follow-up. This eliminates the global system accessors in the current
code while preserving the existing interface.

These are holdovers from Citra and can be removed.

Now that nothing actually touches the internal page table aside from the
memory subsystem itself, we can remove the accessor to it.

Given the page table will always be guaranteed to be that of whatever
the current process is, we no longer need to keep this around.

Centralizes the page table switching to one spot, rather than making
calling code deal with it everywhere.

Keeps the return type consistent with the function name. While we're at
it, we can also reduce the amount of boilerplate involved with handling
these by using structured bindings.

Returns the same type that the function name describes.

Avoids dragging in a direct dependency in a header.

Nothing in this header relies on common_funcs or the memory manager.

This gets rid of reliance on indirect inclusions in the OpenGL caches.

This doesn't actually work anymore, and given how long it's been left in
that state, it's unlikely anyone actually seriously used it.

Generally it's preferable to use RenderDoc or Nsight to view surfaces.

- Fixes graphical issues with Chocobo's Mystery Dungeon EVERY BUDDY!
- Fixes a crash with Mario Tennis Aces

We can just use .at(), which essentially does the same thing, but with
less code.

Given we already ensure nothing can set the zeroth register in
SetRegister(), we don't need to check if the index is zero and special
case it. We can just access the register normally, since it's already
going to be zero.

We can also replace the assertion with .at() to perform the equivalent
behavior inline as part of the API.