Raise error when use_measure_esp not supported

[merav-aharoni]

Summary

Raise error when parameter use_measure_esp=True in IBMBackend.run(), but backend has measure_esp_enabled==False.

Details and comments

See issue #491 .

• I am not sure what the status is with this feature. I saw several relevant tests, so enabled one of them.
• I checked all the backends with
  backends = provider.backends(measure_esp_enabled=True)
  and got [], so I guess no backends support this feature. Is this something planned for the future? Do we want this PR and should I enable the remaining tests?

[coveralls]

Pull Request Test Coverage Report for Build 4984532224

• 1 of 2 (50.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-4.0e**-05%**) to 50.124%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
qiskit_ibm_provider/ibm_backend.py	1	2	50.0%

Totals
Change from base Build 4984333559:	-4.0e-05%
Covered Lines:	3025
Relevant Lines:	6035

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💛 - Coveralls

[kt474]

LGTM! To answer your question, there are currently backends that have measure_esp_enabled set to True so the test that you enabled will now pass.