Introduce new type for operation_metadata_size_limit

⚠ Must be rebased when !6751 (merged) is merged to move the type operation_metadata_size_limit from Block_validation to Shell_limits.

This MR does not change the encoding of the type. Thus a config file with that option is backward compatible.

Context

Make sure that the config file is backward compatible using ./octez-node config init --network sandbox --data-dir ./new --metadata-size-limit 42 before/after the patch and running a node on it before/after.

Closes: #4152 (closed)

Manually testing the MR

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