Deprecate legacy pulse builder command.

[nkanazawa1989]

What should we add?

Pulse builder still supports following commands that inject circuit gate operation into the pulse context:

• qiskit.pulse.builder.call_gate
• qiskit.pulse.builder.cx
• qiskit.pulse.builder.u1
• qiskit.pulse.builder.u2
• qiskit.pulse.builder.u3
• qiskit.pulse.builder.x

These are legacy workflow which we implemented before the pulse gate feature. These command introduce weird cyclic dependency between circuit and pulse program, and must be deprecated before the next release.

In addition, following commands are nice to be deprecated as well.

• qiskit.pulse.builder.active_transpiler_settings
• qiskit.pulse.builder.active_circuit_scheduler_settings
• qiskit.pulse.builder.transpiler_settings

Background

Note that the standard program representation in Qiskit is now QuantumCircuit, and pulse programs exist as a microcode (calibration) of the circuit. The pulse builder is a tool to define such microprograms, and circuit -> pulse conversion must be explicitly done with the circuit scheduler. Injecting circuit instruction in pulse program is indeed an opposite workflow.

[MozammilQ]

@nkanazawa1989 , should I go ahead with this? If I am allowed to?

[nkanazawa1989]

Thanks! I just assigned this to you.

[itoko]

Note: An alternative of pulse.x(q) will be pulse.call(backend.target["x"][(q, )].calibration).

[MozammilQ]

A PR for this seems to be very straight forward, just deprecated these functions, modify tests and add a release note, that's it!
But, for three days I am banging my head over how this is a type: feature request ?
I tried seeing into other issues/comments by Naoki but didn't get any hint.
Anyways, I am opening this PR #11191 with whatever I know, if I left something please guide me :)
@itoko , @nkanazawa1989

[MozammilQ]

@nkanazawa1989 , I think this should be closed isn't it?

[nkanazawa1989]

Right, thanks for the reminder!