Move to natural pom versions

Currently, `${revision}${sha1}` is coded into maven pom files, rendering tools such as jitpack helpless. It would be nice to have normal versions in these files so we have the same chances to use pinot as other java projects. This is particularly important as SNAPSHOT versions are not deployed and docker tags are ad-hoc.

Start by locating the Maven POM files that use ${revision}${sha1} and trace how those values are supplied. Define a consistent natural-version strategy that works for JitPack and avoids SNAPSHOT deployment limitations, then verify that Maven artifacts and Docker tags use the intended versions.

Written by the indexing model from the issue text.