Color matrix defines for filters and identity (#80320)

This PR converts the procs `color_matrix_identity`,
`color_matrix_lightness` and `color_matrix_contrast` into
defines/macros. Also adds in defines for common color matrix filters.

I don't like how `color_matrix_identity` is a one-line proc with no arg.
Also these help people identify the sort of color matrix filter is being
used.

code/modules/admin/view_variables/color_matrix_editor.dm

@@ -12,7 +12,7 @@
 	else if(istext(_target?.color))
 		current_color = color_hex2color_matrix(_target.color)
 	else
-		current_color = color_matrix_identity()
+		current_color = COLOR_MATRIX_IDENTITY
 
 	var/mutable_appearance/view = image('icons/misc/colortest.dmi', "colors")
 	if(_target)

code/modules/admin/view_variables/get_variables.dm

@@ -338,7 +338,7 @@
 
 		if(VV_COLOR_MATRIX)
 			.["value"] = open_color_matrix_editor()
-			if(.["value"] == color_matrix_identity()) //identity is equivalent to null
+			if(.["value"] == COLOR_MATRIX_IDENTITY) //identity is equivalent to null
 				.["class"] = null
 
 		if(VV_INFINITY)