Make parametric controlled operators inherit from ControlledOp

[astralcai]

Context:

Many controlled operations have been added to PennyLane over the years, such as CNOT, CRY, CZ, etc. For code tidiness, we would like to make them all inherit from the ControlledOp base.

Description of the Change:

CRX, CRY, CRZ, CRot, ControlledPhaseShift are now:

1. Moved from pennylane.ops.qubit to pennylane.ops.op_math
2. Inherit from ControlledOp

Calling qml.ctrl on RX, RY, RZ, Rot, and PhaseShift with a single control wire will return gates of types CRX, CRY, etc. as opposed to a general Controlled operator.

The decomposition of an operator created with calling qml.ctrl on RX, RY, RZ, Rot, PhaseShift with a single control wire will now be the full decomposition instead of a single controlled gate. For example:

>>> qml.ctrl(qml.RX(0.123, wires=1), control=0).decomposition()
[CRX(0.123, wires=[0, 1])]

Will become:

>>> qml.ctrl(qml.RX(0.123, wires=1), control=0).decomposition()
[
  RZ(1.5707963267948966, wires=[1]), 
  RY(0.0615, wires=[1]), 
  CNOT(wires=[0, 1]), 
  RY(-0.0615, wires=[1]), 
  CNOT(wires=[0, 1]), 
  RZ(-1.5707963267948966, wires=[1])
]

Benefits:

Code cleanliness.

Related GitHub Issues:

#1447

[trbromley]

Given the size of the diff, could it make sense to split this up into smaller PRs?

[astralcai]

Given the size of the diff, could it make sense to split this up into smaller PRs?

The size of the diff is actually smaller than it looks. We're moving these controlled operators from ops.qubit to ops.op_math, which is probably why it looks like a lot.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (c0ce3ce) 99.68% compared to head (c6694a8) 99.67%.
Report is 6 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5069      +/-   ##
==========================================
- Coverage   99.68%   99.67%   -0.02%     
==========================================
  Files         394      392       -2     
  Lines       35720    35575     -145     
==========================================
- Hits        35609    35460     -149     
- Misses        111      115       +4     

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[timmysilv]

a few little comments, but otherwise this is looking good!

[Alex-Preciado]

Linking to corresponding Shortcut story: [sc-53529]

[albi3ro]

Looks great! 🎉 Thanks for handling all of this :)

[timmysilv]

🕺 🕺