Change (gate, qubits) to GateOperation before act_on_fallback

[daxfohl]

Fixes #4400

@MichaelBroughton noticed during #4371 (comment) that there was some redundancy in act_on_fallback implementations, since each were forced to handle both (gate, qubits) and operations as inputs.

Here we instead only allow Operation as an argument to act_on_fallback, and change a (gate, qubits) tuple to a GateOperation before calling act_on_fallback.

[daxfohl]

Note this is infinite loop safe. If called with GateOperation, GateOperation.act_on calls protocols.act_on(gate, qubits). That then tries gate.act_on, and if that fails will create a new GateOperation and call args.act_on_fallback(gate_op). The only way this could recur infinitely is if act_on_fallback calls protocols.act_on(operation). But if it did, then we'd be experiencing that infinite recursion already.