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...)

find ./Source/ -name '*.cpp' -o -name '*.h' | xargs clang-format-19 -i

The only remaining casts for these types that I know of are in TextureInfo (where format_name is set to the int version of the format, and since that affects filenames and probably would break resource packs, I'm not changing it) and in TextureDecoder_Common's TexDecoder_DrawOverlay, which will be handled separately.

SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.

Migrates off the printf-based formatting where applicable.

This was previously missing for generic (which is used on ARM).