[Enhancements][Cheats] Porting from NES_MISTer

[fjpolo]

I've worked on the cheats system before and beend wanting to implement it for some time now.

Since latest release v0.9 supports a softcore and FATfs it's the right time to bring this one back. I'll work on porting it from MISTer NES core so we can enjoy some dirty cheats

References:

• cheatchodes.sv

[fjpolo]

I'm working in an intermediate step: pipelined wishbone B4, RV will interact with the sb slaves this way

fjpolo/nestang/tree/fjpolo/wishbone

[fjpolo]

In the end I didn't port it from Mister yet, but there's a pre-release with a one-cheat support engine, for those who want to test it:

CheatWizard_1cheatSupport_202040603

My bus and logic need some tweaking before it can work with 4 cheats. Will do it in the next days.

[fjpolo]

PR created: #82

[fjpolo]

Further comments in PR