Add GLES specific setting for layers

This allows loading layers for GLES and Vulkan at the
same time by adding a GLES specific setting:

  GPU_DEBUG_LAYERS_GLES

which mirrors the existing setting:

  GPU_DEBUG_LAYERS

The Vulkan and GLES loaders now scan distinct layer
lists, correcting an issue that would prevent Vulkan
from loading when it failed to find GLES layers.

Bug: 110883880
Test: Load a GLES layer when running ANGLE with Vulkan backend
Test: cts-tradefed run singleCommand cts -m CtsGpuToolsHostTestCases
Change-Id: I370be4ce6fdde9e95989eb1f274add8b5790263e
diff --git a/core/tests/coretests/src/android/provider/SettingsBackupTest.java b/core/tests/coretests/src/android/provider/SettingsBackupTest.java
index 182f189..c298770 100644
--- a/core/tests/coretests/src/android/provider/SettingsBackupTest.java
+++ b/core/tests/coretests/src/android/provider/SettingsBackupTest.java
@@ -451,6 +451,7 @@
                     Settings.Global.ENABLE_GPU_DEBUG_LAYERS,
                     Settings.Global.GPU_DEBUG_APP,
                     Settings.Global.GPU_DEBUG_LAYERS,
+                    Settings.Global.GPU_DEBUG_LAYERS_GLES,
                     Settings.Global.ANGLE_ENABLED_APP,
                     Settings.Global.GPU_DEBUG_LAYER_APP,
                     Settings.Global.ENABLE_GNSS_RAW_MEAS_FULL_TRACKING,