Color map fix region edges

[Xtarsia]

Before:

After:

Also dropping mipmaps for the color maps, as texelfetch wont access them.

Also, this was the last use of uv2 - it is no longer used. making get_region_uv2 redundant as well...

[TokisanGames]

Thank you for fixing these artifacts!

Please also update lowpoly_colormap.gdshader.

Colormap mipmaps are still needed. Try inserting a satellite image on the colormap. It's noisy, especially when moving. If this doesn't apply to the regular, then the colormap debug shader should be adjusted to not use mipmaps.

If uv2 and get_region_uv2 are truly not needed, they can be stripped out.

[Xtarsia]

uv2 gets to live another day! Though i had to remove that 0.5 offset to get things pixel perfect.

new method calculates a region_mip value directly from the derivatives, removing the need for textureQueryLod(), and the bilerp skip is now based off that value instead (log2 of fractional parts is negative, so checking less than 0. for that now.)

added bonus, the color map now blends at regions edges with flat/world noise, side effect of the new method it seems: