feat: Track classical register indices for measurements

Issue #, if available: https://github.com/amazon-braket/amazon-braket-sdk-python/issues/1004

Description of changes: Primarily, instead of discarding the index of a classical register used in an explicit measure assignment (e.g. b[1] = measure q[2];) when building a circuit from OpenQASM using the BDK Interpreter with a ProgramContext instance, the indices are passed into the ProgramContext add_measure method. This change requires all implementations of the ProgramContext class to support a classical_targets parameter in their add_measure method declaration, even if the variable goes unused.

The result of this change addresses the issue attached to this PR, where going to and from Braket circuits and OpenQASM programs will discard classical register indices.

Testing done: Updated test_interpreter.py to verify that classical register indices used in measurements are tracked and stored in order by the default_simulator/circuit/Circuit object when built by the Braket Interpreter,

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amazon-braket / amazon-braket-default-simulator-python