feature: Add get_compiled_circuit convenience method

[laurencap]

Add get_compiled_circuit to GateModelQuantumTaskResult

Issue #, if available:
Closes #780

Description of changes:

Proposed method:

compiled_program = task.result().get_compiled_circuit()

For Rigetti and OQC tasks, this could be used instead of the method described here: https://docs.aws.amazon.com/braket/latest/developerguide/braket-compiled-circuits-inspecting.html

Testing done:
New unit tests, local testing with successful quantum tasks ran on hardware

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (5408783) 100.00% compared to head (63d50e5) 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #787   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files          129       129           
  Lines         8363      8372    +9     
  Branches      1862      1865    +3     
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+ Hits          8363      8372    +9     

Files	Coverage Δ
src/braket/tasks/gate_model_quantum_task_result.py	100.00% <100.00%> (ø)

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[ajberdy]

nit: several of these tests/fixtures can be parametrized with pytest instead of duplicated

[laurencap]

It looks like I should be able to do something like this -- but afaiu parameter inputs can't be fixtures. Do you know how to do it, beyond accepting the fixture name as a string and looking up the function from it? If you have other more specific recommendations please let me know.

@pytest.mark.parametrize("result,program", [(result_rigetti, quil_program), (result_oqc, qasm2_program)])
def test_get_compiled_circuit(result, program):
    """Test get_compiled_circuit method."""
    assert result.get_compiled_circuit() == program

[laurencap]

Updated the result fixtures to reduce duplicated code