Return list[complex] fails when returning list[float]

[amccaskey]

The following fails

import cudaq 

@cudaq.kernel 
def myop(p0 : float, p1: float) -> list[complex]:
    return [0., p0, p1, 0.] 

print(myop)

with

error: type of return operand 0 ('!cc.stdvec<f64>') doesn't match function result type ('!cc.stdvec<complex<f64>>') in function @__nvqpp__mlirgen__myop
RuntimeError: Failure while executing pass pipeline.

we should do some auto-casting from float to complex if the return type is specified like this.