Improve calculation of light colors (#1967)

* maintain precision until all lights are calculated

fixes lugia on the soul silver title screen

* small optimization

* small note

* small cleanup/notes

shouldn't need to check that every time, since the variable shouldn't be able to overflow

* hw doesn't cap difflevel at 255

Should it cap at all?
Can vtx colors overflow...?

* diffuse level appears to be shifted right by 9

fixes some minor inaccuracies

* improve specular lighting a little

* small improvement to diffuse lighting

fixes a few off by ones
- finding by azusa

* small tweaks

* handle overflows of diffuse lighting properly

-credits to azusa once more

* attempt at improving specular lighting calcs

still far from correct, but its a start.
fixes: https://github.com/melonDS-emu/melonDS/issues/1545

* meh

* improve specular lighting further

* add notes

* theory: add half vec instead of subt 1

* implement azusa's specular lighting algorithm

* fix minor edge case with spec lighting

* give proper credit in comments

* fix some bugs/misc tweaks

* more quirky overflow/underflow handling

* fix a spec lighting edgecase

remove some redundant parentheses

* fix an edge case with light vector calcs

* spec recip uses a different calc for light dir?

also remove a check that shouldn't be mathematically possible to trigger

* nvm that thing i thought couldn't trigger was required

also move reciprocal calc into the light vector calc function since i might as well now ig

* replace a bunch of stuff with much *much* simpler algorithms

* misc cleanup

PARENTHESES WOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO

* leave a note abt shininess table's default value being incorrect

src/GPU3D.h

@@ -286,6 +286,7 @@ public:
     s16 Normal[3] {};
 
     s16 LightDirection[4][3] {};
+    s32 SpecRecip[4] {};
     u8 LightColor[4][3] {};
     u8 MatDiffuse[3] {};
     u8 MatAmbient[3] {};