Add config value for a11y color mode

Accessibility transforms require a specific color mode that is not
always available for the user to select.

Bug: 130376719
Test: atest com.google.android.config.pts
Change-Id: If331e663ec50e5507c1e5602e827999ccb6f4dbc
diff --git a/services/core/java/com/android/server/display/color/ColorDisplayService.java b/services/core/java/com/android/server/display/color/ColorDisplayService.java
index 85fb1e0..ad81ca2 100644
--- a/services/core/java/com/android/server/display/color/ColorDisplayService.java
+++ b/services/core/java/com/android/server/display/color/ColorDisplayService.java
@@ -775,10 +775,10 @@
         final ContentResolver cr = getContext().getContentResolver();
         if (isAccessibilityEnabled()) {
             // There are restrictions on the available color modes combined with a11y transforms.
-            if (isColorModeAvailable(COLOR_MODE_SATURATED)) {
-                return COLOR_MODE_SATURATED;
-            } else if (isColorModeAvailable(COLOR_MODE_AUTOMATIC)) {
-                return COLOR_MODE_AUTOMATIC;
+            final int a11yColorMode = getContext().getResources().getInteger(
+                    R.integer.config_accessibilityColorMode);
+            if (a11yColorMode >= 0) {
+                return a11yColorMode;
             }
         }