Scoru_wasm: Parser state encodings

Context

Implements the parser's state encodings.

While it has a lot (A LOT) of code, it is almost completely mechanical: each commit takes one (or two) types from Decode and implements their encoding and the associated tests. It can be easily splitted into multiple MRs.

Depends on !5890 (merged), !5923 (merged) and !5872 (merged)

Owner: @lthms

Manually testing the MR

dune exec src/lib_scoru_wasm/test/test_scoru_wasm.exe : checks the encoding decoding roundtrip of each state.

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