Update documentation and code comments in PowerElectronics module

Summary

Review documentation and comments in the code in PowerElectronics module and make corrections and updates where necessary.

Rationale

The code is nontrivial and providing better documentation would help with its maintenance and adding new features in the future.

Description

A few specific issues to address:

• Update the documentation for evaluateInternalResidual to reference f_int_ in Model/PowerElectronics/CircuitComponent.hpp.
• Use the more verbose name component instead of comp for the component objects in Model/PowerElectronics/SystemModelPowerElectronics.hpp.
• Further document the current structure of f_. The residual vector f_ seems to be still allocated to size_ = n_intern_ + n_extern_, but only the external part (first n_extern_ values) gets updated at the component level.

Additional information

No response