Manifest: generate [tezt/manual_tests/dune]

Context

Removes the alpha client dependency from tezt/manual_tests and generate tezt/manual_tests/dune with manifest.

See the commit history for a rationale for the removal of the alpha client dependency.

Manually testing the MR

dune exec tezt/manual_tests/main.exe -- -f baker_test.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