As means to pave the way for getting rid of global state within core,
This eliminates kernel global state by removing all globals. Instead
this introduces a KernelCore class which acts as a kernel instance. This
instance lives in the System class, which keeps its lifetime contained
to the lifetime of the System class.

This also forces the kernel types to actually interact with the main
kernel instance itself instead of having transient kernel state placed
all over several translation units, keeping everything together. It also
has a nice consequence of making dependencies much more explicit.

This also makes our initialization a tad bit more correct. Previously we
were creating a kernel process before the actual kernel was initialized,
which doesn't really make much sense.

The KernelCore class itself follows the PImpl idiom, which allows
keeping all the implementation details sealed away from everything else,
which forces the use of the exposed API and allows us to avoid any
unnecessary inclusions within the main kernel header.

These conditions are always true, since the outer conditional already
checks for these conditions.

Prompts for title type on NCA files.

i.e. Load the concatenated 00+01 if 01 exists as well. Needed for split NAND NCAs.

Gets the class out of the global namespace.

Full list of new errors and descriptions in core/loader/loader.h

* GDBStub works with both Unicorn and Dynarmic now

* Tidy up

All calling code assumes that the rasterizer will be in a valid state,
which is a totally fine assumption. The only way the rasterizer wouldn't
be is if initialization is done incorrectly or fails, which is checked
against in System::Init().

We move the initialization of the renderer to the core class, while
keeping the creation of it and any other specifics in video_core. This
way we can ensure that the renderer is initialized and doesn't give
unfettered access to the renderer. This also makes dependencies on types
more explicit.

For example, the GPU class doesn't need to depend on the
existence of a renderer, it only needs to care about whether or not it
has a rasterizer, but since it was accessing the global variable, it was
also making the renderer a part of its dependency chain. By adjusting
the interface, we can get rid of this dependency.

Removes leftover code from citra that isn't needed.

None of these files are used in any meaningful way. They're just
leftovers from citra. Also has the benefit of getting rid of an unused
global variable.

General moving to keep kernel object types separate from the direct
kernel code. Also essentially a preliminary cleanup before eliminating
global kernel state in the kernel code.

Makes the global a member of the RendererBase class. We also change this
to be a reference. Passing any form of null pointer to these functions
is incorrect entirely, especially given the code itself assumes that the
pointer would always be in a valid state.

This also makes it easier to follow the lifecycle of instances being
used, as we explicitly interact the renderer with the rasterizer, rather
than it just operating on a global pointer.

- This is necessary so streams are created on the same thread.

* Virtual Filesystem

* Fix delete bug and documentate

* Review fixes + other stuff

* Fix puyo regression

This makes it a compilation error to construct additional instances of
the System class directly, preventing accidental wasteful constructions
over and over.

This would result in a lot of allocations and related object
construction, just to toss it all away immediately after the call.

These are definitely not intentional, and it was intended that all of
these should have been accessing the static function GetInstance()
through the name itself, not constructed instances.

This reverts commit 77c684c1.

* Add VfsFile and VfsDirectory classes

* Finish abstract Vfs classes

* Implement RealVfsFile (computer fs backend)

* Finish RealVfsFile and RealVfsDirectory

* Finished OffsetVfsFile

* More changes

* Fix import paths

* Major refactor

* Remove double const

* Use experimental/filesystem or filesystem depending on compiler

* Port partition_filesystem

* More changes

* More Overhaul

* FSP_SRV fixes

* Fixes and testing

* Try to get filesystem to compile

* Filesystem on linux

* Remove std::filesystem and document/test

* Compile fixes

* Missing include

* Bug fixes

* Fixes

* Rename v_file and v_dir

* clang-format fix

* Rename NGLOG_* to LOG_*

* Most review changes

* Fix TODO

* Guess 'main' to be Directory by filename

LOG_GENERIC usages will be amended in a follow-up to keep API changes separate from
interface changes, as it will require removing a parameter from the relevant function
in the VMManager class.

Converts the service manager from a global into an instance-based
variable.

* core, main.h: Abort on 32Bit ROMs

* main.cpp: Fix Grammar