Allows our CI to catch more potential bugs. This also removes the
[[nodiscard]] attribute of IOFile's Open member function. There are
cases where a file may want to be opened, but have the status of it
checked at a later time.

Recent changes to the build system that made more warnings be flagged as
errors caused building via clang to break.

Fixes #4795

Migrates a remaining common file over to the Common namespace, making it
consistent with the rest of common files.

This also allows for high-traffic FS related code to alias the
filesystem function namespace as

namespace FS = Common::FS;

for more concise typing.

Now that clang-format makes [[nodiscard]] attributes format sensibly, we
can apply them to several functions within the common library to allow
the compiler to complain about any misuses of the functions.

Adds a screenshots directory as a path managed by FileUtil.

It's undefined behavior to pass a null pointer to std::fread and
std::fwrite, even if the length passed in is zero, so we must perform
the precondition checking ourselves.

A common case where this can occur is when passing in the data of an
empty std::vector and size, as an empty vector will typically have a
null internal buffer.

While we're at it, we can move the implementation out of line and add
debug checks against passing in nullptr to std::fread and std::fwrite.

nullptr was being returned in the error case, which, at a glance may
seem perfectly OK... until you realize that std::string has the
invariant that it may not be constructed from a null pointer. This
means that if this error case was ever hit, then the application would
most likely crash from a thrown exception in std::string's constructor.

Instead, we can change the function to return an optional value,
indicating if a failure occurred.

Makes the parameter ordering consistent, and also makes the filename
parameter a std::string. A std::string would be constructed anyways with
the previous code, as IOFile's only constructor with a filepath is one
taking a std::string.

We can also make WriteStringToFile's string parameter utilize a
std::string_view for the string, making use of our previous changes to
IOFile.

The file stream open functions have supported std::string overloads
since C++11, so we don't need to use c_str() here. Same behavior, less
code.

We don't need to force the usage of a std::string here, and can instead
use a std::string_view, which allows writing out other forms of strings
(e.g. C-style strings) without any unnecessary heap allocations.

First of all they are foundamentally broken. As our convention is that std::string is always UTF-8, these functions assume that the multi-byte character version of TString (std::string) from windows is also in UTF-8, which is almost always wrong. We are not going to build multi-byte character build, and even if we do, this dirty work should be handled by frontend framework early.

Uses the C++17 inline variable variants

Prevents compiler warnings.

* Regression and Mode Fixes

* Review Fixes

* string_view correction

* Add operator& for FileSys::Mode

* Return std::string from SanitizePath

* Farming Simulator Fix

* Use != With mode operator&

Avoids unnecessary construction of std::string instances where
applicable.

This avoids a truncating cast on size. I doubt we'd ever traverse a
directory this large, however we also shouldn't truncate sizes away.

Instead of using an unsigned int as a parameter and expecting a user to
always pass in the correct values, we can just convert the enum into an
enum class and use that type as the parameter type instead, which makes
the interface more type safe.

We also get rid of the bookkeeping "NUM_" element in the enum by just
using an unordered map. This function is generally low-frequency in
terms of calls (and I'd hope so, considering otherwise would mean we're
slamming the disk with IO all the time) so I'd consider this acceptable
in this case.

This disallows modifying the internal string buffer (which shouldn't be
modified anyhow).

* Virtual Filesystem

* Fix delete bug and documentate

* Review fixes + other stuff

* Fix puyo regression

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

Without this, it's possible to get compilation failures in the (rare) scenario where
a container is used to store a bunch of live IOFile instances, as they may be using
std::move_if_noexcept under the hood. Given these definitely don't throw exceptions
this is also not incorrect to add either.

Ensure that the actual types being passed in are trivially copyable. The internal
call to ReadArray() and WriteArray() will always succeed, since they're passed a pointer to char*
which is always trivially copyable.

The minimum clang/GCC versions we support already support this. We can also
remove is_standard_layout(), as fread and fwrite only require the type to be
trivially copyable.