Battle Gear 4 Key/RFID + IO Plus emulation

[derole1]

As title says, please see some taito-specific JVS commands that have been emulated which now allow key emulation to work properly with Battle Gear 4 Tuned without memory patches etc.

Two bugs have also been patched to ensure emulation lines up with real Universal JVS I/O packets:

• Watchdog reset response has been changed from 0x00, 0x00 to 0xA0. Real JVS/IO only returns 1 byte not 2 and its always 0xA0
• An exception to the TaitoStick specific response to JvsGetDigitalReply has been added to remove the 4th byte. This should really check the data bytes parameter of the request to determine how many bytes the game wants back, battle gear 4 requests 3 and as TP JVS emulation does not check this for TaitoStick games it will return 4 regardless. This may well fix JVS emulation issues elsewhere too as it invalidates everything after the switch request in the packet (which is the first request in the chain).

With minor modification I would wager this is also applicable to other Taito Universal JVS I/O games (HL2 Survivor etc?).

Raising as a draft to tidy up/add a way to configure the key id, figure out unknown values, as well as ensure I havent broken anything. Would appreciate any comments/feedback! It is fully working in its current state from what I can see.

[derole1]

This PR also addresses issue #960

[derole1]

Requesting a review on this PR. Is pretty much ready and has been tested extensively with a G27 and confirmed 6MT and sequential are both working as expected and all switches etc are also. Valve Limit R (another taito game that uses the same IO config roughly) is also unaffected.

This is with one caveat however. There is a slight bug where you cannot push View and Hazard buttons at the same time, as well as the Overtake button turning the Key switch on (which is inverted by the game).

This existed prior to this PR for SD mode and is due to how TP handles joystick inputs. Essentially TP disallows both Left+Right and Up+Down to be pressed at the same time. This is not an issue with traditional games that use the joystick inputs as intended but when they are used for switches this becomes an issue, especially if two in opposing directions need to be pressed independantly.

I would like some maintainer/developer input here on how best I can work around this before merging. I imagine it is there due to traditional stick JVS games having the joystick physically limit which switches can be pressed (e.g. a joystick cannot physically press left+right or up+down at the same time) however this is not part of the JVS spec and I believe many JVS boards will pass physically "invalid" switch inputs like this without question.

Once this is discussed and PR is merged I will mark the matching OpenParrot PR for review (if the OpenParrot one gets merged before this it will break BG4 tuned pro support).