Allow kwargs in Options

[jyu00]

Summary

Allow users to specify arbitrary kwargs in Options. This PR also creates a new environment section for log_level, image, and instance, as an attempt to reduce the number of first level options.

Details and comments

Fixes #518

In order for auto-complete work as before, Options remains a dataclass. The new _flexible decorator dynamically creates a new dataclass with the additional fields. The new dataclass also inherits the original, so any isinstance call would continue to work.

[coveralls]

Pull Request Test Coverage Report for Build 3123362114

• 99 of 103 (96.12%) changed or added relevant lines in 5 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-2.0%) to 62.207%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
qiskit_ibm_runtime/qiskit_runtime_service.py	12	13	92.31%
qiskit_ibm_runtime/runtime_options.py	7	8	87.5%
qiskit_ibm_runtime/options.py	76	78	97.44%

Files with Coverage Reduction	New Missed Lines	%
qiskit_ibm_runtime/options.py	1	87.05%

Totals
Change from base Build 3100068626:	-2.0%
Covered Lines:	3190
Relevant Lines:	5128

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💛 - Coveralls

[kt474]

LGTM!