Add EstimatorV2Converter and BackendEstimatorV2

[ikkoham]

Summary

Add EstimatorV2Converter and BackendEstimatorV2 to qiskit.primitives.
EstimatorV2Converter converts an instance of BaseEstimatorV1 into an instance
of BaseEstimatorV2. BackendEstimatorV2 is simple conversion of BackendEstimator
that inherits BaseEstimatorV1.

[coveralls]

Pull Request Test Coverage Report for Build 8098602282

Details

• 69 of 73 (94.52%) changed or added relevant lines in 3 files are covered.
• 17 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.007%) to 89.296%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
qiskit/primitives/backend_estimator.py	21	25	84.0%

Files with Coverage Reduction	New Missed Lines	%
crates/qasm2/src/lex.rs	5	91.44%
crates/qasm2/src/parse.rs	12	96.69%

Totals
Change from base Build 8097968633:	0.007%
Covered Lines:	59180
Relevant Lines:	66274

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💛 - Coveralls

[qiskit-bot]

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

• @Qiskit/terra-core
• @ajavadia
• @ikkoham
• @levbishop
• @t-imamichi

[1ucian0]

Should this PR be updated after #11931 merged ?

[t-imamichi]

This PR currently includes 1) a converter from EstimatorV1 to Estimator V2 and 2) a backend Estimator V2.
The second one was already addressed by #11931. So, we need to discuss whether we want to merge a converter 1).

• Pros: it might be useful if only Estimator V1 is available, e.g., AerEstimator.
• Cons: we need to maintain the converter.

The discussion may depend on how many Estimator V1 implementations available.

[1ucian0]

In discussion with others in the core team about the EstimatorV1-to-EstimatorV2 converter (and general PrimitiveV1-to-PrimitiveV2):

• There is value in this kind of converters for users and primitives implementors
• Aer should natively implement primitives in the long run, without converters
• Converters from PrimitivesV1 should live until PrimitivesV1 gets removed

Let's close this PR and move this conversation to issues for primitive converters: #12047 #12046