Reduce dependence on GateWithRegisters

[mpharrigan]

This class implements both the Bloq interface as well as the cirq.Gate interface (simultaneously). The factored way of doing this is to implement the Bloq interface and use the to-cirq functionality (including Bloq.on()) to explicitly access the cirq.Gate interface.

In theory, most places where algorithms descend from GateWithRegisters, it can be migrated to just Bloq as the superclass with minimal changes. These changes include:

• if the gate overrides decompose_from_registers (i.e. cirq-style decomposition), you must add an explicit override

    def decompose_bloq(self) -> 'CompositeBloq':
        return decompose_from_cirq_style_method(self)

• If the gate overrides circuit_diagram_info, you can use qualtran.cirq_interop._cirq_to_bloq._wire_symbol_from_gate or just implement the wire_symbol method (preferred)

[mpharrigan]

The name GateWithRegisters is somewhat unhelpful. History: I picked this name when it was literally just a cirq gate with names for the registers :) . A better name would indicate its true role as a cirq.gate/qualtran.bloq hybrid. But separating these concerns is the better medium+ term solution.

[mpharrigan]

This issue can be used to track places where porting GateWithRegisters to Bloq is non-trivial.