[FEATURE] Add support for ctrl gate modifier

[TheGupta2012]

Feature Description

openqasm3 defines the ctrl quantum gate modifier on arbitrary quantum gate operations. Current support is only for the inv and pow modifiers but having support for arbitrary control modifiers would be pretty cool!

Implementation (Optional)

It might not be very straightforward to implement arbitrary controlled gate operations. For reference, we can see how qiskit's synthesis library does the decomposition. It will be good to do some digging there before starting with implementation as I am not entirely sure if it can be done without ancillas OR that it handles every arbitrary gate.

• First, we should see what all support is present in qiskit and try to get some inspiration from their synthesizers.
• Build implementation for ctrl @ which only uses 1 qubit as control AND gates from basic gate set.
• Expand this 1-qubit control to custom gate support
• Once we have this basic MWP, we can look to expand it and start thinking about arbitrary controlled gate compilation -
  • multi control
  • multi target
  • minimizing ancillas