use pulse_alignment from Target in PadDynamicalDecoupling

[ajavadia]

Summary

The intent for the Target argument in transpiler passes is that they will supply the necessary information for passes to use. There was an oversight when adding this for the PadDynamicalDecoupling pass, where users still had to separately pass pulse_alignment even though this information is contained in the Target. This commit is a simple fix of that oversight.

Details and comments

[qiskit-bot]

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

• @Qiskit/terra-core

[coveralls]

Pull Request Test Coverage Report for Build 7726869440

• 0 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• 13 unchanged lines in 3 files lost coverage.
• Overall coverage decreased (-0.004%) to 89.548%

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Files with Coverage Reduction	New Missed Lines	%
crates/qasm2/src/expr.rs	1	93.81%
crates/qasm2/src/lex.rs	6	91.44%
crates/qasm2/src/parse.rs	6	97.62%

Totals
Change from base Build 7674621352:	-0.004%
Covered Lines:	59586
Relevant Lines:	66541

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💛 - Coveralls

[TsafrirA]

With the proposed fix, if the user provides both pulse_alignment and target, the pulse_alignment argument will be ignored (the same was and is true for the durations argument). I think this is counter intuitive and should be reflected to the user somehow.

[mtreinish]

Yeah, I agree this should update the docstring to reflect that target will supersede pulse_alignment if set (like it currently does for the other arguments).

[ajavadia]

I updated the docstring to make this clear. I believe this is the behavior across the board (in all passes target takes precedence).

[mtreinish]

Thanks for updating the docstring too. I agree this is consistent with how target is handled in other passes too