Autotune memory

[jsoref]

Public runners have ~10G of ram available.

XL runners have >50G of ram available.

It's nice to be able to run tests on public runners.

Introduce an action that:

• (Linux) frees some memory
• (Linux) adds some swap
• (Linux and macOS) calculates available memory
• (Windows) suggests 10G of available memory

https://docs.github.com/en/code-security/codeql-cli/codeql-cli-manual/test-run#-m---rammb

This addresses https://github.com/github/codeql/pull/15471#issuecomment-1919283105

Note that the shooting services isn't strictly necessary and could easily be omitted.

Afaict, Windows isn't actually used, but it seemed to make sense to at least provide something.

The workflows also had some incorrect dependencies which I'm cleaning up here.