Nested bool contexts give unexpected results

[achidlow]

Currently, entering a "bool context" (for example, the target of an if condition, or explicitly converting something to bool via bool(...)) is not properly handled when nested occurs.

from puyapy import Bytes, Contract, UInt64, op

class Oopsie(Contract):
    def approval_program(self) -> bool:
        empty = Bytes()
        one = UInt64(1)
        return bool(op.bitlen(empty or one))

    def clear_state_program(self) -> bool:
        return True

This will give the error message:

error: Invalid argument type "bool" for argument "a" when calling puyapy.op.bitlen

This is incorrect, it's a type union not a bool. We allow type unions in a bool context explicitly, in this case it should warn that it's not supported (a further improvement is to actually support this particular case, which is feasible since the underlying op code supports the type union).