Proto: clean frozen deposits

Context

We gave up on cleaning frozen deposits in Oxford 2 but we can do (most of) it in P.

fix #6798 (closed) fix #6683 (closed)

Manually testing the MR

TODO:

• on a mainnet context, check that frozen deposits are indeed (mostly) cleaned
• check it doesn't take too much time

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR