Kaitai: CI job for semantic validation of generated `ksy` files

Context

Follows !10864 (merged) and requires opam-repository!464 (merged), part of #6629.

Implements automate-semantic-validation-as-part-of-the-ci:2.2.2.

Follow-up

• !10966 (merged) (wip) - Add input for e2e semantic testing of ground kaitai generated specs.

Manually testing the MR

CI should pass. We are interested in a new kaitai_e2e_checks job in particular here.

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