User overloadable unitary modifiers (dagger, control, power)

[ss2165]

It is assumed there is some mechanism for automatically daggering, quantum controlling or powering (repeating) unitary subroutines. This may be higher order, with blocks. See #158 #361 etc.

Users should also be able to specify specialist implementations of these.

I propose using dunder methods for this:

@guppy_unitary
class MyOracle[N: int]:
    param: int # can be parametric instances
    __impl__(self, q: array[qubit, N]):
        ...
    __control__(self. q: array[qubit, N], ctrl: qubit):
        ...
    # dagger and power are still default

[NathanCQC]

For context, this was one of the features users really enjoyed in qlibs regarding the speed of algorithm development.

[NathanCQC]

I will happily review this PR.

[jake-arkinstall]

Extension request: provide __control__sqrt__ and __control_sqrt_inv__ to enable an arbitrary number of control qubits via recursion.