[Feature] Add user-facing option to retrieve IR instead of API object

[dominikandreasseitz]

from qadence2_expressions.core import compile, irc

phi = symbol("phi")
expr = RX(phi / 2)(1) * RY(phi / 2)(2)

# this compiles into IR and then into the native backend
api = compile(expr, backend='pyqtorch') 
wf = api.run()
expval = api.expectation()

#in case the user wants to debug or inspect the IR which is used to compile into the API object
ir_repr = irc(expr)

print(ir_repr)
>>>Model(
  register=AllocQubits(
    num_qubits=3,
    qubit_positions=[],
    grid_type=None,
    grid_scale=1.0,
    options={},
  ),
  inputs={},
  instructions=[
    Assign('%0', Call('mul', 0.5, Load('phi'))),
    QuInstruct('rx', Support(target=(1,)), Load('%0')),
    QuInstruct('ry', Support(target=(2,)), Load('%0')),
  ],
  directives={},
  settings={},
)

tagging @Roland-djee @Doomsk too

For debugging purposes
https://jax.readthedocs.io/en/latest/_autosummary/jax.make_jaxpr.html