Add clifford gates to collect_cliffords (backport #12750)

[mergify]

Summary

This PR adds some Clifford gates to the CollectClifford() transpiler pass.

Details and comments

This is an immediate bugfix which does not handle the following problems:

• When adding a gate to the Clifford class, it should be added in other places of the code,
  and there is no single list of gates that the Clifford class supports.
  

  qiskit/qiskit/transpiler/passes/optimization/collect_cliffords.py

  Line 27 in 6b57b78

  class CollectCliffords(CollectAndCollapse):

  
  and
  

  qiskit/qiskit/circuit/random/utils.py

  Line 290 in fa3d6df

  def random_clifford_circuit(num_qubits, num_gates, gates="all", seed=None):

• The current Clifford class can handle certain u gates (for certain angles), and this does not appear in the docs, neither in the code above:
  

  qiskit/qiskit/quantum_info/operators/symplectic/clifford_circuits.py

  Line 100 in fa3d6df

  if isinstance(gate, Gate) and name == "u" and len(qargs) == 1:

---

This is an automatic backport of pull request #12750 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 41267ec has failed:

On branch mergify/bp/stable/1.1/pr-12750
Your branch is up to date with 'origin/stable/1.1'.

You are currently cherry-picking commit 41267ecf5.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   qiskit/transpiler/passes/optimization/collect_cliffords.py
	new file:   releasenotes/notes/fix-collect-clifford-83af26d98b8c69e8.yaml

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   qiskit/circuit/random/utils.py

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[qiskit-bot]

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• @Qiskit/terra-core

[coveralls]

Pull Request Test Coverage Report for Build 9894614827

Details

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• 37 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.05%) to 89.916%

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Files with Coverage Reduction	New Missed Lines	%
crates/qasm2/src/lex.rs	7	91.86%
crates/qasm2/src/parse.rs	30	95.77%

Totals
Change from base Build 9860435060:	-0.05%
Covered Lines:	61828
Relevant Lines:	68762

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💛 - Coveralls