Create a function for checking whether all instructions in a quantum circuit are unitary

[caleb-johnson]

What should we add?

There are many places in Qiskit where each instruction in a quantum circuit is checked to determine if it is unitary. Unify this logic under one function, rather than writing various individual loops for checking data.

More conversation here in #11177 .

[saketpab]

hi @caleb-johnson, may I be assigned this task

[caleb-johnson]

hi @caleb-johnson, may I be assigned this task

I think this should be a straightforward task, but I don't have permissions to assign issues. I'm sure @jakelishman wouldn't mind you working on this :)