Fix transpile() with a Target containing an ideal Measure

[mtreinish]

Summary

This commit fixes an oversight in the transpile() function when running with a Target (either directly or via a backend) that contains a Measurement operation that is ideal (either globally or locally) with no properties defined. This was not handled correctly in the function used to convert a Target to a BackendProperties payload for passes that are not yet target aware and this would cause an exception to be raised. This commit fixes this edge case and excludes readout properties from the generated BackendProperties in this case.

Details and comments

Fixes #8969

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[coveralls]

Pull Request Test Coverage Report for Build 3342757244

• 5 of 5 (100.0%) changed or added relevant lines in 1 file are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.07%) to 84.486%

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Files with Coverage Reduction	New Missed Lines	%
qiskit/extensions/quantum_initializer/squ.py	2	79.78%

Totals
Change from base Build 3342084476:	0.07%
Covered Lines:	62157
Relevant Lines:	73571

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💛 - Coveralls

[itoko]

LGTM, thank you for the quick fix. I left one minor comment inline. It's a nitpick, so not worth blocking the merge.

[itoko]

This may be a too small nitpick in the original code, but these lines suggest we cannot mix ideal Measures and real Measures (if do that, real Measures will be silently converted to ideal Measures here, right?). Warning here (or allowing the mixture) might be nice. That said, I don't think of any practical use case of such a mixture, so I'm fine with keeping the code as is until we encounter any concrete issue.

[mtreinish]

That's a good point, I do think it's unlikely in practice for there to be mixed ideal and real measurements but we should try to support that especially since it's possible combination and allowed in the target. The only reason we have to special case measurement here is because it's special in BackendProperties.