WASM: forbid floats at kernel decoding

Context

This MR forbids the usage of float values at during the parsing (decoding) phase. This is quite a straightforward MR, but it needs a bit a review to ensure that we actually trap every float instruction.

Fixes #4393 (closed)

Manually testing the MR

To check floats are not trapped outside of the PVM:

make test-webassembly

To check floats are actually trapped by the PVM:

dune exec src/lib_scoru_wasm/test/test_scoru_wasm.exe -- test "Init"

Note that these tests are a bit poor, and could use a generator to check every instruction is trapped.

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