Add system capabilities variable that tracks individual features instead of broad emulator support

[someone2639]

Addresses #652
for 2.4 both systems will coexist

Need clarification on the following checks (especially whether they're useful for any game devs):

• DMA timings
• RSP pipeline stall timings
• Certain 64-bit mode behaviors

[someone2639]

The ticket mentions selfcheck features that would simply crash some emulators (such as emux support); would like to know if there's a feature-set that guarantees we're not on a crashing emulator to test this (if not, we couldn't deprecate gEmulator even if we wanted to).

[someone2639]

Officially blocked because I don't know how to do the rest of the things in the ticket

But if those are unnecessary, then this is ready for review 🏇

[gheskett]

That's fine, just throw a HackerSM64 TODO at the commented flags and we can defer the rest of the issue to 3.0

[someone2639]

i forgor software framebuffer support, will handle today™

Update: handled™

[gheskett]

Can you reference the ranked implementation? I think this is the cleanest way to handle it (though you may have to set the capability outside of that function)

[someone2639]

ready for another lap 🏇