Enable retrieval of historical data for 'target'

[merav-aharoni]

Summary

Allow the user to retrieve historical data for the target of the backend.

Details and comments

This is similar to the support that already exists for backend.properties. For target, we defined a new method - target_history, since target is defined as a property.
Note that when we try to pass the datetime parameter to defaults(), it does not work, because there is no support for this parameter on the server side.
See similar support in Qiskit/qiskit-ibm-provider#535.

[coveralls]

Pull Request Test Coverage Report for Build 4377189123

• 2 of 9 (22.22%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.07%) to 66.707%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
qiskit_ibm_runtime/ibm_backend.py	2	9	22.22%

Totals
Change from base Build 4377079329:	-0.07%
Covered Lines:	3300
Relevant Lines:	4947

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💛 - Coveralls