GH-139596: Cease caching config.cache & ccache in GH Actions

[AA-Turner]

This removes the config.cache and ccache caches from GitHub Actions. Note that we still install and use ccache via posix-deps-apt.sh, so we will get the benefit from that still (if any), but we will no longer save it to the GHA cache.

A

• Issue: Caching config.cache in GitHub Actions is unsafe #139596

[mhsmith]

For future reference:

• config.cache is removed because Caching config.cache in GitHub Actions is unsafe #139596.
• ccache is removed because it wasn't giving much benefit, and it may become even less useful when GitHub more strictly enforces the cache size limit.

[mhsmith]

Can we also remove config-hash from reusable-context.yml?