Bump pe-pse and re-enable promotions (Puppet Platform 7.16.0)

(Initial planned release date: 2022-04-12)

If this release is not destined for an upcoming PE release, you can close this ticket.

Otherwise, once PE release branches have been cut:

• Bump the version of pe-puppet-server-extensions such that the X and Y versions match those of the subsequent PE release but the Z and build versions are bumped/reset, so that we have somewhere to branch from if we need to promote anything to the PE release branches.
  For example:
  • 2019.8.3.96-SNAPSHOT -> 2019.8.4.0-SNAPSHOT
  • 2021.4.0.66-SNAPSHOT -> 2021.5.0.0-SNAPSHOT
• Re-enable puppetserver promotions