ImDebugger: Minor issues to fix

[hrydgard]

• Trying to change breakpoints when running can hang the emulator, due to WaitInactive. This is a misdesign caused by the assumption that breakpoint modifications are not coming from the main thread (which was valid in the old and web debuggers).
• Add sensible UI for the function hash+replacement stuff. Currently a buggy setting FuncHashMap is all that's available, and it often writes bogus data.
• Stepping by "Draw" seems to double-increment the prim counter