Add resilience.zne.amplifier to EstimatorV2 options

[ihincks]

Summary

This PR adds the ZneOptions attribute amplifier which can be one of these strings:

• "gate_folding" (default) uses 2-qubit gate folding to amplify noise. If the noise
  factor requires amplifying only a subset of the gates, then these gates are chosen
  randomly.
• "gate_folding_front" uses 2-qubit gate folding to amplify noise. If the noise
  factor requires amplifying only a subset of the gates, then these gates are selected
  from the front of the topologically ordered DAG circuit.
• "gate_folding_back" uses 2-qubit gate folding to amplify noise. If the noise
  factor requires amplifying only a subset of the gates, then these gates are selected
  from the back of the topologically ordered DAG circuit.

Details and comments

Fixes #1670

[coveralls]

Pull Request Test Coverage Report for Build 9101350749

Details

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.002%) to 82.765%

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Totals
Change from base Build 9084268669:	0.002%
Covered Lines:	6238
Relevant Lines:	7537

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💛 - Coveralls

[jyu00]

We'll need to add this to the schema as well, cc @gadial