[WIP] Make RVGate a standard gate

[mtreinish]

Summary

This commit moves the RVGate from the generalized gate module and makes it a standard gate. This involves defining it as a standard gate in Rust so that there is an efficient representation of the gate in rust like the other standard gates.

This is step 1 towards reimplementing the synthesis from #6048 in modern qiskit. The next PR after this will implement RV gate as a supported basis target in the one qubit decomposer.

Details and comments

TODO:

• Fix definition for parametrized gates
• deprecate basis argument on constructor
• add missing versor implementation
• Add tests to explicitly verify parameterexpression definition path is correct

[qiskit-bot]

One or more of the following people are relevant to this code:

• @Cryoris
• @Qiskit/terra-core
• @ajavadia

[mtreinish]

FWIW, I'm aware these don't handle the denominator being negative correctly. But there isn't a way in a parameter expression to know at this point. This probably means we can't do it this way or come up with a different formula to go from rv -> u. But I spent the time to type all this out before realizing it so I wanted to push it up at least in a draft before reverting to this path returning None instead of a circuit.

[Cryoris]

Is #6048 still something we want? What are it's applications? (pinging @ajavadia since you opened the original PR 😄)

[jakelishman]

Julien: we can't accept the API changes of #6048 (see #6048 (comment)), but we kept the PR open so there was an easy handle to the synthesis, which is valid and a fine addition. It's quite nice in principle to have both Euler-angle and axis-angle decompositions accessible by default, even if we don't use the latter much.

[ShellyGarion]

There are now many tranpiler passes in rust that have hard-coded lists of standard gates (see e.g. #15047 and #15502), so it's worth to check how this will impact them.