fix: Support single-register measurements in `from_ir`

Issue #, if available: Currently, the statement b = measure q in an OpenQASM program results in the following error:

ValueError: Operator qubit count 1 must be equal to size of target qubit set QubitSet([Qubit(0), Qubit(1)])

This is because a measure instruction is always a 1 qubit instruction but right now, all the targets get added to the measure instruction even if there are more than 1 qubit measured.

To reproduce this issue:

bell_qasm = """
OPENQASM 3;

qubit[2] q;
bit[2] c;

h q[0];
cnot q[0], q[1];

c = measure q;
"""

from braket.circuits import Circuit
print(Circuit.from_ir(bell_qasm))

Description of changes:

Add a loop to add a single measure instruction for each qubit target.
Add a test to prevent this error in the future

Testing done: tox and tox -e integ-tests

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amazon-braket / amazon-braket-sdk-python