Feature: option to replace the base class of generated registers

[Furetur]

In this issue, I propose a new feature which has been requested by my coworkers and would simplify their RTL-testing routines. I am planning on adding this feature myself. Here, I aim to discuss the feature with the project's authors and get the necessary approval.

Motivation

My coworkers want to collect coverage information in our RAL-based UVM tests. The easiest way of doing this seems to involve replacing the base class of generated registers (uvm_reg) with a custom class myreg and implementing the coverage-related logic there:

Proposal

I propose adding a special CLI option: --reg-base-class with default value of uvm_reg. This option regulates which base class is used for generated register classes:

class {{get_class_name(node)}} extends {{reg_base_class}};

If --reg-base-class=myreg is passed then all generated registers inherit from myreg

[Furetur]

@amykyta3 could you please give your opinion on this matter?