[Capture] unitary_to_rot is plxpr compatible

[andrijapau]

Context:

This PR adds a UnitaryToRotInterpreter to apply the unitary_to_rot transform natively to plxpr.

Description of the Change:

• Add UnitaryToRotInterpreter to transform plxpr

Benefits:

unitary_to_rot can be applied natively to plxpr.

import jax
import pprint

qml.capture.enable()

U1 = qml.Rot(1.0, 2.0, 3.0, wires=0)

@qml.capture.expand_plxpr_transforms
@qml.transforms.unitary_to_rot
def f(U1):
    qml.X(0)
    qml.QubitUnitary(U1, 0)
    qml.Y(0)
    return qml.expval(qml.Z(0))

>>> jaxpr = jax.make_jaxpr(f)(U1.matrix())
>>> tape = qml.tape.plxpr_to_tape(jaxpr.jaxpr, jaxpr.consts, U1.matrix())
>>> pprint.pprint(tape.operations)
[X(0),
 RZ(Array(1., dtype=float32), wires=[0]),
 RY(Array(2., dtype=float32), wires=[0]),
 RZ(Array(3., dtype=float32), wires=[0]),
 Y(0)]
>>> pprint.pprint(tape.measurements)
[expval(Z(0))]

Possible Drawbacks: None identified.

[sc-83556]

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.59%. Comparing base (67fbcba) to head (ea4a582).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #6916   +/-   ##
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  Coverage   99.59%   99.59%           
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  Files         480      480           
  Lines       45520    45547   +27     
=======================================
+ Hits        45335    45362   +27     
  Misses        185      185           

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[mudit2812]

Implementation looks good. I'll do a second pass later to review tests.

[mudit2812]

Pretty much ready to approve. Could you add a test to verify that using @unitary_to_rot with @qml.capture.expand_plxpr_transforms works correctly? Check out this PR for a good example