Previously, a branch would be deployed as `archive` even if it had a
major version that was equal/higher than that of the stable branch (as
long as it was not the RC branch - i.e. not the most recent minor
branch). For example, with `11.0.x` as the stable branch and `12.0.x`
as the RC branch, `11.1.x` would be deployed as archive.
Theoretically, we should never find ourselves in such a situation.
Typically, there will only be at most one minor branch most recent than
the stable one (and that branch will be the RC branch). However, it
is possible under unusual circumstances.
This commit adds additional checks to guard against this problem. It
also refactors the code in preparation of fixing an issue with
`rc.angular.io` redirects in the presence of a ServiceWorker, which will
require identifying whether there is an active RC version or not.
See #39760 for more details.
PR Close#39853