What should we add?

Sub-epic of #9417.

This is the list of issues needed to support control flow at optimisation level 2 in transpile.

Depends on:

• Support control flow in SabreSwap #9419
• Support control flow in Python components of SabreLayout #9421
• Support control flow in CommutationAnalysis and CommutativeCancellation #9423

Once all the dependants are satisfied (add more to the list as they're found), the error-on-control-flow pass in the run initialisation for optimisation level 2 should be dropped to close this issue: https://github.com/Qiskit/qiskit-terra/blob/e981b7e8ba073388edc3544b30d908b731dc6d7d/qiskit/transpiler/preset_passmanagers/level2.py#L247-L249