Extract ccache in github actions as an external reusable actions

[vicentebolea]

WIP

[Copilot]

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.github/workflows/everything.yml:65

• Ensure that prefixing with './' does not unintentionally exclude files matched by '*-changed-files.txt' that might reside in other directories.

ls -la ./*-changed-files.txt

.github/workflows/everything.yml:181

• [nitpick] Verify that the key value aligns with the internal logic of both custom actions, as they prepend 'ccache-' to the key. This consistency is important to ensure proper cache hit behavior.

key: ${{ matrix.os }}-${{ matrix.compiler }}-${{ matrix.parallel }}${{ matrix.shared == 'static' && '-static' || ''}}