Remove comparable_ty

Context

Merge ty and comparable_ty. It will avoid conversions between both, which reduces the time and memory consumptions.

See the preparatory work:

• !4133 (merged)
• !4506 (merged)
• !4507 (merged)
• !4658 (merged)
• !4659 (merged)
• !4692 (merged)
• !4693 (merged)

In this MR, the comparable_ty type is removed and all ..._key constructors are replaced by the ..._t constructors.

The change is safe if and only if the comparable flag of ty is correct (see !4693 (merged)), which you can check in Script_typed_ir.

The MR is split by file (in the order given by TEZOS_PROTOCOL) so only the last commit compiles. I can squash everything on merge if you think it's better.

What will follow: getting rid of redundant stuff:

• !4721 (merged)
• !4722 (merged)
• !4723 (merged)

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