Add more I/O read tests

[KellanClark]

Tests for almost every non-serial I/O register between 0x4000100 and 0x4000160 along with DISPCNT, Green Swap, SOUNDBIAS, WAITCNT, and IME.
Be warned the DISPCNT and Green Swap tests cause a little flickering when looking at their results. I am 100% open to feedback on anything to remove or change.
All results verified on a 3DS.

[endrift]

I have an (unpushed) commit that adds many of these, but individual tests for dozens of registers that don't exist is more or less fluff and not actually useful. That said, for flickering reasons, the display registers are absent, and for "I'm not sure if this will break things", the timer and IRQ registers are absent too.