LinSrgba, Srgba and Hsla color types

[lassade]

The bevy 0.5 made colors operations undefined, this directly affects our ability to animate any color property.

There is a ongoing discussion here about this.

So this PR does the following:

1. Adds LinSrgba, Srgba, Hsla color types.

Using colors as types allows for predictable behaviour, easer readability, compile time optimizations:

// Lerp happens in HSL space but result is stored as sRGB
// a is converted to HSL, b is a HSL, 2 conversions are made (just count the into calls)
let c: sRGB = HSL::lerp(a.into(), b, 0.5).into(); 

When conversions from SRGB to HSL and back to SRGB are done often, cache the HSL;

2. type Color = LinSrgba

By default the renderer should operate in the linear color space so we define the Color type to be in this same space, to avoid any unnecessary conversions;

3. Fixes color constants for both LinSrgba and Srgba,

I just used a python script to convert the color constants between each space;

[mockersf]

Before this, I think we should agree on wether to roll our own colors, use palette, use kolor or rgb

[lassade]

I made this PR, because I really want to animate colors and to make easier to test out this approach (which, I think is the best), so nothing is set stone.

I think roiling with our own type is simpler because we can implement any conversions or traits we want;

If you notice I aligned the colors to 16 bytes so they can be ready to use with simd instructions (SSE2), thats because I assumed everything have a alpha, and that is not something I saw in any other crate;

Plus I'm thinking in using the kolor crate (once it's ready), because it allows to use our own storage types while having theirs conversions methods;

[mockersf]

Sound good to me, I would just like to avoid a breaking change in colors in 0.6 and in 0.7. But even that is not a blocker, we offer no guarantee on that... Breaking twice before 0.6 should be ok.

@kabergstrom when do you feel kolor could be ready?

[kabergstrom]

I think it's getting there, I added HSV/HSI/HSL, ICtCp and CIELuv this weekend. Did some more work on the docs. What would you like to see in the library?
I need to write the readme, set up CI and add better reference unit tests.

[lassade]

I'm blocked by some animator system stuff before I can do some more testing about colors. Do way I think adding using kolor won't break anything, will just add more color types;

[NathanSWard]

For floating-point equality checks, should we be using some sort of epsilon or a different crate like float-cmp?

[alice-i-cecile]

#4648 contains further design direction on color. It's probably going to be easier to start from scratch, but I'll leave that decisison to you.

[nicopap]

Superseded by #12013