Adds logic for determining active LTS branches for a given
release configuration. The active LTS branches can be determined
by querying NPM and matching dist tags against a specific
pattern. i.e. `v{major}-lts`.
This logic will be useful for the release tool that supports
publishing of active LTS version branches.
PR Close#38656
We initially added logic for determining active release trains into
the merge script. Given we now build more tools that rely on this
information, we move the logic into a more general "versioning" folder
that can contain common logic following the versioning document for the
Angular organization.
PR Close#38656