Implement a Pixel FIFO / Don't Draw Entire Scanline at HBLANK

[torch2424]

That way we can render our scanlines and respect any changes as we go along our cycles, rather than waiting until X cycles, and then drawing the entire scanline.

[torch2424]

Pixel FIFO is mentioned in the ultimate gameboy talk and see #33 for why this would improve our accuracy :)

[torch2424]

Woaahhhh There's a new really cool doc on the pixel fifo: https://github.com/corybsa/pandocs/blob/develop/content/pixel_fifo.md

Huge thanks to @BlueBlazin for sending this over, and @corybsa for writing this up! 😄 👍

Also, my work here is already like 75% done on the https://github.com/torch2424/wasmboy/tree/graphics-rewrite-pixel-fifo branch.

[corybsa]

No problem. I find the lack of documentation on the FIFO unsettling. I am very unfamiliar with the graphics system of the Game Boy so my write-up should be taken with a grain of salt (or two). I basically just studied SameBoy for 2 weeks and tried to document what it does. We've asked Liji to review it, so whenever he has some free time hopefully we can finally get some good documentation on the FIFO.