Improve adapter debugger state

[tracktwo]

The current debugger state (normal, busy, various waits) are super ad hoc and rely on the fact that only a single thread is communicating from the adapter side. Even then there are probably races as the atomic may not be sufficient to synchronize all cases, and the event signaling system is also pretty hacky.

These should be unified so cases where the handler needs to wait for a process to complete (e.g. add breakpoints waiting for the breakpoint response back from unreal) are easier to use and won't introduce races.