Allow writing to Genesis Registers

[getCursorsExe]

[YoshiRulz]

For reference: https://github.com/TASEmulators/BizHawk/blob/2dae3505d7d68fe8d2898b31319f8df98411f88e/src/BizHawk.Emulation.Cores/Consoles/Sega/gpgx64/GPGX.IDebuggable.cs#L36-L40

[nattthebear]

Unlikely to be very useful without single step debugging

[kaithar]

Hypothetically... if this were functional, would it work as expected if an event hook (say, an execute hook) fired off a SetCpuRegister write to the PC to effectively force an immediate jmp? Or would something else get in the way?

[YoshiRulz]

By convention, hooks fire immediately before the read/write/exec, so I'd expect it would jump once it gets execution back from the callback. But that would be an implementation detail, and without an implementation I can't say.