Fixes: KartKrew/Kart#1405

Gitlab CI improvements

See merge request KartKrew/Kart!2385

Like with ccache, we want to make sure the git checkout is considered
clean during build.

Placing these directories at the root will make the git revision
detection consider the working directory to be dirty.

Instead of using the install baked in the image, let's clone vcpkg
and set up a separate binary cache that can survive being cleaned.
This allows us to reuse built artifacts from the vcpkg manifest
baseline very quickly.

Let's not rely on the CMakeLists.txt to automatically detect and
use ccache. It's better to just explicitly specify it.

The "clone" strategy clones the entire repository, which takes
a significant amount of time. It's not needed, because the default
"fetch" strategy will reuse the executor's local clone and clean it
before the job scripts run.

There's no need to let these artifacts pile up since the only ones that
will be relevant to non-programmers are the latest from any given ref.

Ring Racers' object file output is considerably larger than SRB2.
50M is insufficient to hold even a single build.

The singular .gitlab-ci.yml is pretty beefy. Splitting it into
smaller files by job and job template will make maintaining the
individual jobs easier.

PostThinkFrame during run only

See merge request KartKrew/Kart!2383

It's scary that it wasn't doing this before!

This ensures that the build system won't output something like
ringracers_rr/master.exe, among other potential issues.

Update vcpkg baseline, remove libvpx overlay

See merge request KartKrew/Kart!2324

Use rapidjson master in discord-rpc

See merge request KartKrew/Kart!2376

The last stable version of rapidjson was in 2016, and it is
unlikely that neither rapidjson nor discord-rpc will receive a
stable release ever again. However, rapidjson has a lot of fixes
merged in their tree, so in order to fix gcc 14 compilation issues,
let's pull in that tree.

The upstream changes for libvpx on Windows were merged and so this
overlay is no longer needed.

Updating the baseline requires everyone to update their vcpkg repo
locally (git pull). It also upgrades all dependencies used.

Don't allow auto-roulette to get challenging items

See merge request KartKrew/Kart!2367

Only apply maxconnections to bots in netgame contexts

See merge request KartKrew/Kart!2366

Shorten fault void time by about 1 second for position pitfalls

See merge request KartKrew/Kart!2362

Allow better steering from trick MT release

See merge request KartKrew/Kart!2352

G_GetNextMap: More ironclad behaviour for encore update deferral

See merge request KartKrew/Kart!2334

GP naming

See merge request KartKrew/Kart!2365

UFO determination

See merge request KartKrew/Kart!2355

Burger deflection

See merge request KartKrew/Kart!2364