Fix dt units in test util function convert_to_target

[kevinhartman]

Summary

Previously, convert_to_target was reading dt from the configuration/conf file, expecting it to be in seconds, when it is actually in nanoseconds.

The effect of this was that FakeBackendV2 targets would return a InstructionDurations with all durations as 0, since all durations round to 0 when divided by the erroneously large dt and converted to an integer.

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[mtreinish]

Good catch, this lgtm. Just one comment on the release note and a suggestion on the unit test.

[mtreinish]

LGTM, thanks for fixing this

[coveralls]

Pull Request Test Coverage Report for Build 2247717376

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• 3 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.005%) to 84.323%

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Files with Coverage Reduction	New Missed Lines	%
qiskit/pulse/library/waveform.py	3	89.36%

Totals
Change from base Build 2236086132:	-0.005%
Covered Lines:	54518
Relevant Lines:	64654

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💛 - Coveralls

[HuangJunye]

@kevinhartman Good catch. I thought I corrected the error when I made the FakeBackendV2 PR #7643 but actually introduced another error...

a814fa7#diff-eb1c104ba5abb83f1ab8c8b159c2b5537b234aca17a448fa15cbc55d0461ece7L85-R109

qiskit-ibm-runtime has its own copy of backend_converter.py. It should be updated too. CC @rathishcholarajan