Draft: Michelson: ignore all annotations but entrypoints

Context

Fixes metastatedev/tezos#113, #155 (closed)

TZIP: tzip!138 (closed)

TODO:

• Check annotations are well formatted when parsing non-legacy code, this is to prevent breaking tools expecting ASCII-only annotations
• Make entrypoint type private, reuse rafoo_'s MR
• add -v to our exiting typechecking tests and add the result to the regression testing traces. (!2482 (comment 491613567))

Manually testing the MR

Use automatic tests

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Provide automatic testing (see the testing guide).
• Add item in the Development Version section of CHANGES.md (only for new features and bug fixes).

Reviewers

• @rafoo_ @yrg
• people from higher-level languages teams