refactor(debugger): modularize and add a context struct

[DaniPopes]

Motivation

• Clearly split the two event loop phases of the debugger (process & draw) into separate files
• Create a context to hold the debugger state and use it in processing

No functional changes. Follow-up required to refactor drawing to use the context as well.

Best reviewed commit-by-commit and with "hide whitespace". I've tried my best to keep commit diffs readable.

Solution

[onbjerg]

better