Add debug test

Created by: silabs-PaulZ

Adding a basic debug test in the core/debug_test directory.

• It will test debug and trigger CSR access from main code and debugger code
• Ensure ebreak from main code launches proper exception handler
• Launch debug_req signal and start debugger code
• Ensure ebreak call while the core is in debug_mode will restart debugger code
• Basic trigger test, causing entry into debug_mode when matching specific address