Set version number to 0.22.0rc1 for first release candidate

[mtreinish]

Summary

For the 0.22.0 release we're going to push release candidates prior to the release to enable testing before we cut the final release. In preparation for tagging the first release candidate this commit updates the version string to indicate it's a release candidate. This commit should be what gets tagged as 0.22.0rc1.

Details and comments

[qiskit-bot]

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[coveralls]

Pull Request Test Coverage Report for Build 3205700382

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 29 unchanged lines in 6 files lost coverage.
• Overall coverage decreased (-0.04%) to 84.719%

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Files with Coverage Reduction	New Missed Lines	%
src/sabre_swap/sabre_dag.rs	1	94.44%
qiskit/extensions/quantum_initializer/squ.py	2	79.78%
src/optimize_1q_gates.rs	2	93.55%
qiskit/pulse/library/waveform.py	3	91.49%
src/results/marginalization.rs	7	84.48%
src/sampled_exp_val.rs	14	63.93%

Totals
Change from base Build 3205699351:	-0.04%
Covered Lines:	61871
Relevant Lines:	73031

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💛 - Coveralls

[mtreinish]

We're finally ready to merge this and tag the rc1 after #8849 merges

[jakelishman]

I'll hold off tagging this automerge until #8849 has actually merged, just in case that fails CI from flaky VMs or something.