[Do Not Merge] PRE application contract (full)

[vzotova]

Type of PR:

• [X] Feature

Required reviews:

• [X] 3

What this does: Implements PRE contract as Threshold application

Notes for reviewers: Based on #2824

[vzotova]

Do you plan to open a corresponding PR in to nucypher/nucypher-contracts? Doing so will help to front load the transition.

Yes, but there will be one commit only (probably) so I guess here will be easier to review. I'm planning to maintain this PR for a while

[KPrasch]

obsoleted by #3227