Temporarily remove Operation class usage for 0.20

[eliarbel]

This PR temporarily removes Operation from being a base class for various circuit element types due to the performance degradation found in #7528 and given the fact that the Operation class intent is still not utilized in QuantumCirctuit.append

Summary

Details and comments

[eliarbel]

Properties inherited from Operation (such as name, num_qubits are left untouched in Instruction, CNOTDihedarl, Clifford and Pauli.

[mtreinish]

Do you want to drop this here? This means we're not re-exporting the Operation class from the root qiskit.circuit. This will limit who has access to the class. I'm fine with that as we're saying for 0.20.0 we added the class but nothing uses it yet. Just wanted to make sure that was the intent

[eliarbel]

Yes, Matthew, I think it's better this way before we re-add it in way that solves #7528

[mtreinish]

This LGTM, thanks for doing this. Is there something we still need to do here to remove the WIP, I personally don't see anything missing from it.

[eliarbel]

Nothing else to do, I was waiting for the CI to finish (my lint + tests are still running locally, nice to see how fast those servers are :-) ). WIP removed

[coveralls]

Pull Request Test Coverage Report for Build 2064899040

• 13 of 13 (100.0%) changed or added relevant lines in 9 files are covered.
• 16 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.01%) to 83.744%

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Files with Coverage Reduction	New Missed Lines	%
qiskit/pulse/library/waveform.py	3	89.36%
qiskit/circuit/operation.py	13	0%

Totals
Change from base Build 2064574046:	-0.01%
Covered Lines:	53150
Relevant Lines:	63467

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💛 - Coveralls