Initial integration for debug_test

This PR does the following:

1. Connects the debug_req_i of the core to the debug virtual peripheral.
2. Updates files in the debug_test test-program to suit the CV32E20 and hopefully (?) improve read-ability.

Note that there are also a large number of formatting changes to the test-program files such as replacing tabs with spaces - this makes the changes to these files appear much larger than they actually are.

Currently, not all tests in debug_test are passing, so the test-program is deliberately ended early. This PR will remain a draft until all tests are passing.