Add standard 1q Pauli equivalences to standard library

[jakelishman]

Summary

This makes transpile a little more reliable in cases where people are trying to use it to convert to a constrained basis. We can't necessarily recognise all possible transformations into an incomplete basis, but simple Pauli relations are things people may well expect.

Details and comments

Fix #10293.

[qiskit-bot]

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

• @Cryoris
• @Qiskit/terra-core
• @ajavadia

[mtreinish]

LGTM, this is a straightforward addition to the standard equivalence library that makes sense to have.

[jakelishman]

Helps if I remember to use the opt_level test parametrisation that I set up, haha.

[coveralls]

Pull Request Test Coverage Report for Build 5289644275

• 12 of 12 (100.0%) changed or added relevant lines in 1 file are covered.
• 15 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+0.001%) to 85.94%

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Files with Coverage Reduction	New Missed Lines	%
crates/qasm2/src/lex.rs	1	91.14%
qiskit/extensions/quantum_initializer/squ.py	2	80.0%
crates/qasm2/src/parse.rs	12	96.65%

Totals
Change from base Build 5284896987:	0.001%
Covered Lines:	71348
Relevant Lines:	83021

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💛 - Coveralls