Tezt: Remove Baker module from tezt tests

What

Closes #7773 (closed).

Parent MR: !17294 (merged)

Why

Since the protocol-specific baker binaries will become soon obsolete, we remove the Baker module from tezt, as it relies on them.

How

By removing the Baker module from Tezt, together with any uses of the protocol dependent baker binaries (Protocol.baker protocol).

Manually testing the MR

CI green and more specifically:

dune exec tezt/tests/main.exe -- --file protocol_migration.ml

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