gpu_thread: Use the previous MPSCQueue implementation

service: irs: Implement clustering processor

applet/swkbd: Implement optional symbol keys 

exit gracefully on sigint/sigterm

chore: make yuzu REUSE compliant

As mentioned in the previous commit, `reuse lint` can be used to ensure
that copyright information is always present and up to date.

This adds a GitHub Action that does just that, using the official
fsfe/reuse-action

[REUSE] is a specification that aims at making file copyright
information consistent, so that it can be both human and machine
readable. It basically requires that all files have a header containing
copyright and licensing information. When this isn't possible, like
when dealing with binary assets, generated files or embedded third-party
dependencies, it is permitted to insert copyright information in the
`.reuse/dep5` file.

Oh, and it also requires that all the licenses used in the project are
present in the `LICENSES` folder, that's why the diff is so huge.
This can be done automatically with `reuse download --all`.

The `reuse` tool also contains a handy subcommand that analyzes the
project and tells whether or not the project is (still) compliant,
`reuse lint`.

Following REUSE has a few advantages over the current approach:

- Copyright information is easy to access for users / downstream
- Files like `dist/license.md` do not need to exist anymore, as
  `.reuse/dep5` is used instead
- `reuse lint` makes it easy to ensure that copyright information of
  files like binary assets / images is always accurate and up to date

To add copyright information of files that didn't have it I looked up
who committed what and when, for each file. As yuzu contributors do not
have to sign a CLA or similar I couldn't assume that copyright ownership
was of the "yuzu Emulator Project", so I used the name and/or email of
the commit author instead.

[REUSE]: https://reuse.software

Follow-up to 01cf05bc

externals: Use GitHub for FFmpeg

FFmpeg's own git repo seems to be down, so switch to GitHub like we use
for most externals.

yuzu, network: Add room service and UI configuration

Co-Authored-By: Narr the Reg <5944268+german77@users.noreply.github.com>

yuzu: Streamline broken Vulkan handling

kernel: use KScheduler from Mesosphere

service: irs: Add camera support, split processors and implement ImageTransferProcessor

There was a bug where, when using the numeric keyboard, moving between buttons resulted in an infinite loop, resulting in a stuck state.
This was due to prev_button being the only one enabled in that row or column, causing the condition in the while loop to always be true.
To fix this, detect whether we have returned to that initial row/column and break out of the loop.

These are only used in the numeric keyboard, and correspond to the keys to the left and right of the "0" key on the numeric keyboard.