Scripts: use `slim-mode.sh` instead of `re{move,store}-old-protocols.sh`

This MR is based on !13471 (merged) and !13477 (merged).

What

This MR modifies CI scripts to use:

• scripts/slim-mode.sh on instead of scripts/remove-old-protocols.sh
• scripts/slim-mode.sh off instead of scripts/restore-old-protocols.sh

It also removes the following files:

• scripts/remove-old-protocols.sh
• scripts/restore-old-protocols.sh
• `script-inputs/active_testing_protocol_versions'

Why

The slim mode script is simpler, faster, and achieves the same result. In particular the list of protocols that are removed by the two approaches happens to be exactly the same. There is no need to maintain the two approaches.

Scripts remove-old-protocols.sh and restore-old-protocols.sh are now unused and can be removed.

Script input file active_testing_protocol_versions is now unused and can be removed. It was only used by remove-old-protocols.sh.

How

One noteworthy feature is that remove-old-protocols.sh had an optional path parameter to move the deleted files to this path instead of deleting them. This allowed restore-old-protocols.sh to restore the files. With slim mode this is not useful.

In fact, one of the scripts moved deleted protocols to a directory named .trash, which surprises me because I would expect dune to still see those files.

Manually testing the MR

CI should pass.

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