Make Helm artifacts reproducible

[potiuk]

Following #36726, #36744, #36763, #36819 this PR adds the feature of
making source tarball that we release as an official release of
the ASF for Helm Chart into reproducible tarball. This means that
anyone should be able to produce such tarball using the sources
of airflow and verify that he tarball pushed to SVN by the
release manager is built from our source repositories.

We also do the same with Helm package. It turns out that gpg signing
of the package does not modify the .tgz file - it just adds .prov file
containing checksum and signature, so we can safely re-pack the .tar.gz
package in a reproducible way, this way we have both reproduciblity and
provenance check nicely working together.

There are few changes in this PR that are related:

• Bumped Helm version in our environment to use the latest one and
  using the breeze k8s setup-env environment to run all the release
  commands - this way we can be sure same helm version is used to build
  the package, further making it more reproducible.

• The reproducible packaging utility we have has been refeactored now -
  we take "source" archive as parameter rather than directory and simply
  repack it in reproducible way.

• The tool also applies group/other ownership removal on its own,
  because helm package has no option to umask the generated files.

• In this change we also ignore subcharts from being exported to the source
  tarball package as we shoudl not include source files from postgres in
  our source package..

• Both - the tarball and helm package are generated in dist folder similarly as
  all our other packages.

• Documentation for releasing the packages and verifying them is updated.

• CI jobs are updated to use the new commands and generated packages are
  produced as artifacts so that we can be sure the commands continue
  working and produce the right output.

---

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[potiuk]

cc: @jedcunningham - I'd love you take a look before preparing the Helm Chart to see if that all looks good for you - I made all the variables and package location quite a bit more consistent. Also the source tarball contained postgres.tgz which I think it should not - users can download them on their own and we should not release those sources together with ours IMHO.

[potiuk]

I actually managed to get also the helm package reproducible - It turned out to be as easy as repackaging the .tar.gz produced by helm-package in a reproducible way. Signing the packages with helm-gpg does not change the package itself, it only adds .prov file, so we can re-package the produce .tar.gz and use helm gpg to generete .prov.

This way we can nicely combine reproducible packages, signing in ASF way and signing with .prov file. Pretty cool.