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: I9902fe7921a171cd779fd7dd957dd51e00b4ef02
diff --git a/libs/graphicsenv/GraphicsEnv.cpp b/libs/graphicsenv/GraphicsEnv.cpp
index 8661401..97b4828 100644
--- a/libs/graphicsenv/GraphicsEnv.cpp
+++ b/libs/graphicsenv/GraphicsEnv.cpp
@@ -153,10 +153,18 @@
     return mDebugLayers;
 }
 
+const std::string& GraphicsEnv::getDebugLayersGLES() {
+    return mDebugLayersGLES;
+}
+
 void GraphicsEnv::setDebugLayers(const std::string layers) {
     mDebugLayers = layers;
 }
 
+void GraphicsEnv::setDebugLayersGLES(const std::string layers) {
+    mDebugLayersGLES = layers;
+}
+
 android_namespace_t* GraphicsEnv::getDriverNamespace() {
     static std::once_flag once;
     std::call_once(once, [this]() {