After the merge of #18331, the packaged source tarball is created by git archive, but the binaries are built from another one which is made by make dist.
With this PR the only source tarball, created by git archive, is used both for binaries building and for packaging to users.
As a good side-effect, #18349 becomes redundant.
Change in behavior
The following variables https://github.com/bitcoin/bitcoin/blob/1b151e3ffce7c1a2ee46bf280cc1d96775d1f91e/configure.ac#L2-L6
are no longer used for naming of directories and tarballs.
Instead of them the gitian descriptors use a git tag (if available) or a commit hash.
Also a small refactor commit picked from #18404.