[Refac] Merge `run` and `run_dm` in the backends

[EthanObadia]

This issue includes several tasks for refactoring and adding noise in Qadence:

Merge run and run_dm in the backends:

• [x] Remove the run_dm method from the abstract class Backend, the Horcrux, Bracket and Pyqtorch classes..
• [x] Merge the run_dm and run methods in the Pulser backend class.
• [x] Modify the unpyqfy method to represent the output density matrix as tensor. Closes #428

Add the noise gates from pyq:

• [x] Add an optional noise parameter to the PrimitiveBlock class
• [x] Add an optional noise parameter to the ParametricBlock class
• [ ] Update the Primitive and Parametric block instances class to support the noise attribute.
• [x] Add pyq's protocols to the Noise Class.
• [ ] Modify the convert_block function:
• [ ] Add a constructor in pyq: Closes #423

Add the noise features:

• [ ] Create a function to add a noise protocol after every gate in a circuit.
• [ ] Create a function to add a noise protocol after a specific type of gate in a circuit. (Will open an issue)