Yellow squiggly lines begone!
Done automatically on .cpp files through `run-clang-tidy`, with manual corrections to the mistakes.
If an import is directly used, but is technically unnecessary since it's recursively imported by something else, it is *not* removed.
The tool doesn't touch .h files, so I did some of them by hand while fixing errors due to old recursive imports.
Not everything is removed, but the cleanup should be substantial enough.
Because this done on Linux, code that isn't used on it is mostly untouched.
(Hopefully no open PR is depending on these imports...)

Check if the return value of std::filesystem::remove_all is -1 rather
than 0; the former is the specified return value if there's an error
while 0 just means the directory already didn't exist (which is the end
result we want).

Previously error messages such as the following were possible:
E[COMMON]: DeleteDirRecursively: [path]/User/RedirectSession/ failed The
operation completed successfully.

Also adds a period in the error string to make it look nicer.

Logic and structures are largely taken from Linux source:
drivers/bluetooth/btusb.c
drivers/bluetooth/btrtl.c
drivers/bluetooth/btrtl.h

Unlike custom banners which work as an override, this mechanism works as
a fallback. The use case is if you have games you don't really play but
want to keep around for testing purposes without filling up your NAND
with lots of saves. For ease of use, the directory structure is the same
but only title/$title_hi/$title_lo/data/banner.bin files are
relevant.

It was being done manually, which a TODO comment advised against.
Using generic_string() from std::filesystem::path solves this.

Fix encoding issue using generic_wstring instead.