Update Tezt to version 4.0.0

Context

Corresponding MR: opam-repository!465 (merged)

Tezt 4.0.0 has been released on opam. This MR brings this new version to Octez.

Tezt 4.0.0 has some breaking changes in the Cli module so some small fixes where needed.

Tezt 4.0.0 now uses Clap instead of Stdlib.Arg, and this means that the existing test that itself used the Arg module breaks. The fact that it even worked was pure luck, by the way. Anyway, I ported the command-line argument of this test to Clap to make it work. This makes the command-line argument appear in --help, which is nice.

In the Manifest, I added the constraint: tezt < 5.0.0, to avoid future breaking changes (see https://github.com/ocaml/opam-repository/pull/24785 and !10834 (merged)).

All changes in Tezt were approved or LGTM'd by two Tezos devs before being merged into Tezt (the approvals sometimes disappeared though because rebasing removes them in Tezt's repository). Full changelog here: https://gitlab.com/nomadic-labs/tezt/-/blob/master/CHANGES.md

Manually testing the MR

Trust the CI, play with Tezt. For instance, look at the new --help:

dune exec tezt/tests/main.exe -- --help

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