gdk: Add oklab and oklch color states

These are new default color states.

Tests for the tf and matrices included.

testsuite/gdk/colorstate-internal.c

@@ -23,6 +23,7 @@ TransferTest transfers[] = {
   { "hlg",     hlg_oetf,     hlg_eotf,     { 0, 1}, { 0, 1} },
   { "gamma22", gamma22_oetf, gamma22_eotf, { 0, 1 }, { 0, 1 } },
   { "gamma28", gamma28_oetf, gamma28_eotf, { 0, 1 }, { 0, 1 } },
+  { "oklab",   to_oklab_nl,  from_oklab_nl,{ 0, 1 }, { 0, 1 } },
 };
 
 #define LERP(t, a, b) ((a) + (t) * ((b) - (a)))
@@ -103,6 +104,8 @@ static MatrixTest matrices[] = {
   { "ntsc", ntsc_to_xyz, xyz_to_ntsc },
   { "p3", p3_to_xyz, xyz_to_p3 },
   { "srgb<>rec2020", rec2020_to_srgb, srgb_to_rec2020 },
+  { "oklab<>lms", oklab_to_lms, lms_to_oklab },
+  { "lms<>srgb", lms_to_srgb, srgb_to_lms },
 };
 
 #define IDX(i,j) 3*i+j