feat: add cache-optimized option for timestamp-based caching

[castler]

Adds a new cache-optimized input that, when enabled, uses timestamp-based cache keys instead of file hashes for disk and repository caches. Old caches are automatically deleted via the GitHub Actions Cache API before saving new ones.

[NEOatNHNG]

Duplicate of #163 ?

[titusfortner]

I didn't even see this one before doing mine. Does my PR solve your underlying problem, or is there something more you want specifically from timestamp-based caches?

[castler]

I didn't even see this one before doing mine. Does my PR solve your underlying problem, or is there something more you want specifically from timestamp-based caches?

Sorry, I was on sick leave.

For what I can say, I think your PR also solves my (our) problem.
I still think it is weird to create a hash over the BUILD files as identification, since it is fairly possible that the BUILD files stay the same, but the bazel cache changes (e.g. a cpp or python or what ever file changed). In that situation we would with your solution delete the old cache and upload a new one with the same hash. To avoid this, I switched to timestamps for the hash, instead of creating a hash over files.

I am not sure if this can have negative impacts, but I doubt. So I am also fine with your solution.

[castler]

In order to cope with our requirements, we needed a more complex setup which we documented here:
https://github.com/eclipse-score/communication/blob/b3874c07d3fe7201eb7ca60b3fd6edc0df006aa3/.github/cache-strategy.md

Since this requires a very tight integration with the workflows used within a project - I do not believe this is of general usage and thus does not make sense to place into setup-bazel.

Thanks to @p0deje for the feedback he gave for this and similar PRs - which uncovered some hickups!