Remove era prefix from all rule names

[lehins]

After #5826 it is no longer necessary and in fact redundant to have a prefix every rule to be prefixed with era name, eg. Shelley.ShelleyPPUP.

This ticket is about removing era prefix from all rules from. Thanks to #5826 it should be possible to do this task with AI or simple sed without a single compilation failure. However, because it is a breaking change we need add three commits that:

1. Rename ledger rule type, eg.

   -data ShelleyDELEG
   +data DELEG

2. Add a type synonym with deprecation pragma, eg.

   type ShelleyDELEG = DELEG
   {-# DEPRECATED ShelleyDELEG "In favor of `DELEG`" #-}

3. Record those renames in the changelog.