Fix UnitarySynthesis pass bug when target contains global gates (backport #13651)

[mergify]

Summary

While working on #12850 I realized that the UnitarySynthesis Rust implementation would sometimes append non-2q-gates to the basis set and panic over the dimension mismatch. I had assumed that target.operation_names_for_qargs(Some(&qubits)) would only return gates whose number of qubits matched len(qubits), but this assumption is incorrect. It will return any gate with some overlap with the provided qargs, independently of the number of qubits of the gate. This bug would come up often when the target contained global gates.

I believe that the fix is as simple as making sure the 2q basis contains only 2q gates, at least for the cases I found.

Details and comments

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This is an automatic backport of pull request #13651 done by [Mergify](https://mergify.com).

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[coveralls]

Pull Request Test Coverage Report for Build 12752410944

Details

• 4 of 4 (100.0%) changed or added relevant lines in 1 file are covered.
• 14 unchanged lines in 3 files lost coverage.
• Overall coverage decreased (-0.01%) to 88.921%

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Files with Coverage Reduction	New Missed Lines	%
crates/accelerate/src/two_qubit_decompose.rs	1	91.96%
crates/qasm2/src/parse.rs	6	97.62%
crates/qasm2/src/lex.rs	7	91.98%

Totals
Change from base Build 12709260875:	-0.01%
Covered Lines:	79159
Relevant Lines:	89022

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💛 - Coveralls