Multi-Tool Support (Questasim, Xcelium, VCS) and Unified Compilation Flow for cvfpu-uvm

Summary

This PR modifies the existing Python parser files for the compilation, simulation and regression flows with a new version that supports Xcelium and VCS in addition to the already supported Questasim.

Key Changes

• New versions for compile.py, run_test.py and run_reg.py for supporting the commands introduced by the new supported tools Xcelium and VCS.
• A general refactoring of the Python code: no more multi-layer yaml files needed. Single .f file approach has been adopted.
• New Python parser post_proc.py introduced for having a single command that can perform post-processing analysis for all of the three tools.
• New template for top yaml files and deletion of get_cmd.py since its functionalities have been included in the other python files.
• Slight modification of some sv files for compatibility with all of the three compilators. Some SV constructs such the use of an object class inside a virtual interface is not supported by Xcelium

CVFPU-UVM Tested

The modifications introduced by this PR have been used with the ones introduced in the analogous PR of https://github.com/openhwgroup/cvfpu-uvm.git for the cvfpu-uvm testbench. The coupled use of both the PRs works for cvfpu-uvm