change tar.gz to tgz to match helm releaser, add helm for git hash, u…

[amitschang]

This PR addresses two things:

• There is some inconsistency between how the release helm chart is published and the PR/main commits, the publication tool writes to .tgz extension, whereas other was publishing to .tar.gz, since we have easier control over the non-release, this commit just updates to match the release extension.
• We publish images tagged with the commit hash, so we should also publish helm charts using those tags. These tags are more stable than using a name such as main (which constantly changes). This commit adds that