[BUG] pyqasm.unroll() handling of include statements

[ryanhill1]

Right now, pyqasm.unroll() seems to be adding an include "stdgates.inc" statement to all programs, even if the original qasm program didn't have it. This is problematic when using together with a library that doesn't support "include" statements, e.g. Amazon Braket:

from braket.circuits import Circuit
from braket.circuits.serialization import IRType
from braket.ir.openqasm import Program

from pyqasm import dumps, loads

bk_bell = Circuit().h(0).cnot(0, 1).measure(0).measure(1)

qasm_str = bk_bell.to_ir(IRType.OPENQASM).source

program = Program(source=qasm_str)

# Reconstruct the original Circuit from QASM string - this works as expected
circuit = Circuit.from_ir(source=program.source, inputs=program.inputs)

module = loads(qasm_str)

module.unroll()

qasm_unrolled = dumps(module)

program_unrolled = Program(source=qasm_unrolled)

# Attempt to reconstruct a Circuit from the unrolled QASM string - this raises a FileNotFoundError
# Error: FileNotFoundError: [Errno 2] No such file or directory: 'stdgates.inc'
circuit_unrolled = Circuit.from_ir(source=program_unrolled.source, inputs=program_unrolled.inputs)

The include "stdgates.inc" statement should only be added to the unrolled qasm if it was present in the original, input program.

Another related issue, let's say I unroll a qasm string with 2 custom include statements:

from pyqasm import dumps, loads

custom_qasm = """
OPENQASM 3.0;
include "customgates.inc";
include "othergates.inc";
bit[2] b;
qubit[2] q;
h q[0];
cnot q[0], q[1];
b[0] = measure q[0];
b[1] = measure q[1];
"""

module = loads(custom_qasm)

module.unroll()

qasm_unrolled = dumps(module)

OPENQASM 3.0;
include "stdgates.inc";
bit[2] b;
qubit[2] q;
h q[0];
cx q[0], q[1];
b[0] = measure q[0];
b[1] = measure q[1];

Using pyqasm.unroll() all existing include statements are overwritten by include "stdgates.inc";, which shouldn't happen.