CI: cache deb and rpm for month

[ostinru]

Cache CPU-heavy CI steps:

• DEB build
• RPM build

This should speed up our CI pipelines and reduce github actions quota usage.

Implementations details:

• Github cache has 7 days TTL. Every build will reset expiration timeout. In order to force CI to build cloudberry from time to time - I am explicitly specifying current month in a cache key.
• keep both: actions/cache and actions/actions/upload-artifact. In case cache eviction happens during build (e.g. hit 10Gb limit) we will still have running builds.
• cache reused between main and other PRs (but not between PRs). So, cache will be filled only during builds in main.

[ostinru]

Mostly it is copy-paste from our old PXF. So, I would expect that this should work fine.
https://github.com/open-gpdb/pxf/blob/MDB_STABLE/.github/workflows/ci.yml