Proto/Michelson: improve regularity of parse_data

Context

This MR makes parse_data more regular by aligning the atomic cases of crypto types (BLS, Sapling, and timelocks) with the other atomic types. In particular:

• Invalid_syntactic_constant errors are added where appropriate in the error traces, and
• parse_* functions are added for these cases.

These were discovered while working on !10211.

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