[3.12] gh-113858: GH Actions: Make ccache smaller (GH-113859, GH-113945)

[encukou]

This backports 3 PRs:

• GH-113858: GitHub Actions config: Only save ccache on pushes #113859

  Only save ccache on pushes

• gh-113858: Cut down ccache size #113945

  Cut down ccache size

  • Only save the ccache in the main reusable builds, not on builds that
    don't use special build options:
    • Generated files check
    • OpenSSL tests
    • Hypothesis tests
  • Halve the max cache size, to 200M

• gh-113858: GH Actions: Limit max ccache size for the asan build #114113

  Fixup for the above

• Issue: ccache GitHub action generates excessive caches #113858

[miss-islington-app]

Thanks @encukou for the PR 🌮🎉.. I'm working now to backport this PR to: 3.11.
🐍🍒⛏🤖

[miss-islington-app]

Sorry, @encukou, I could not cleanly backport this to 3.11 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 74485c0323f91b32877e71c233570d89bc63fbd5 3.11

[bedevere-app]

GH-114188 is a backport of this pull request to the 3.11 branch.