Track QuantumCircuit.global_phase in ParameterTable

[jakelishman]

Summary

We have previously always had a split where circuit parameters used in instructions were tracked in the ParameterTable, but any parameters used in the global phase were not. Any method that influenced the parameters needed to separately check the global phase, and merge that information with that in the ParameterTable. This made it easy to forget, or easy for the handling of it to become out of sync.

This commit now tracks the global phase as part of the ParameterTable, so this object is now the canonical source of parameter information for the circuit (outside the context of calibrations, which are handled entirely separately). The ParameterTable is an internal detail, and only accessible through private attributes, so is not part of the public interface.

Details and comments

Dependent on #11109, which this PR currently includes. I'll rebase it after that merges, but I'm putting this up a little early just to have things to link to in the dependency chain of #7107.

No changelog because it's a dev-only internal detail (in theory).

[qiskit-bot]

One or more of the the following people are requested to review this:

• @Qiskit/terra-core

[coveralls]

Pull Request Test Coverage Report for Build 7280677428

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A quick fix for this PR: rebase it; your next report should be accurate.

• 37 of 45 (82.22%) changed or added relevant lines in 2 files are covered.
• 104 unchanged lines in 5 files lost coverage.
• Overall coverage decreased (-0.02%) to 87.536%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
qiskit/circuit/quantumcircuit.py	26	27	96.3%
qiskit/circuit/parametertable.py	11	18	61.11%

Files with Coverage Reduction	New Missed Lines	%
qiskit/circuit/library/standard_gates/u3.py	1	98.9%
qiskit/circuit/bit.py	3	91.49%
crates/qasm2/src/lex.rs	7	91.16%
crates/accelerate/src/quantum_circuit/circuit_data.rs	8	90.71%
qiskit/circuit/quantumcircuit.py	85	91.39%

Totals
Change from base Build 7263539836:	-0.02%
Covered Lines:	59174
Relevant Lines:	67600

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💛 - Coveralls

[jakelishman]

Now rebased over #11109.

[ElePT]

From my (less limited than a few hours ago, but still limited) understanding, I don't see any functional issue with this implementation. It might not be the most straightforward, manual intervention is needed in a few points to make sure that the global phase is tracked properly (for example in copy), and this is adding responsibility to the developers (to keep on top of these details). But at the same time, I cannot come up with any concrete feedback or suggestions to improve it. I will approve to make sure this PR is not blocked, but it might be worth having somebody else give it some thought too.

[jakelishman]

Yeah, that's pretty much how I felt writing it as well, haha. I don't like what I've done hugely, but I don't have any better ideas, and overall this makes parameter-handling code more local.

[kevinhartman]

LGTM.

I'll need to update #11214 once this merges to handle parameter remapping in circuit_to_instruction.

Approving but holding off on merge in case addressing my comment warrants any code change. Feel free to merge as is.

[kevinhartman]

LGTM, thanks!