Improve the GDB debugging session output

[mithro]

It would be good to improve the GDB debugging sessions in the workshop.

• [ ] It would be good to have a pygments Lexer for GDB
• [ ] Demonstrate connecting to Fomu.
• [ ] Demonstrate connecting to Renode.
• [ ] Demonstrate loading programs directly into memory.
• [ ] Demonstrate loading programs debug symbols.
• [ ] Demonstrate setting breakpoints and then resuming.
• [ ] Demonstrate single stepping.