Move flag feature_overrides to namespace "gpu"

Move the aconfig feature flag "feature_overrides" from the
"core_graphics" namespace to "gpu".

Note: This necessitates a new flag name as well:

go/aconfig-namespace#aconfig-namespaces-2
> Once a flag's declaration is merged, its namespace cannot be changed.
> If you've assigned the incorrect namespace, rename the flag and assign
> the correct namespace in the same change.

Due to this, the name is being changed to "angle_feature_overrides".

Old:
  com.android.graphics.graphicsenv.flags.feature_overrides
New:
  com.android.graphics.graphicsenv.flags.angle_feature_overrides

Bug: 372694741
Test: aflags list | grep angle_feature_overrides
Test: aflags enable com.android.graphics.graphicsenv.flags.angle_feature_overrides
Flag: com.android.graphics.graphicsenv.flags.angle_feature_overrides
Change-Id: Idc859b76b846901e1e763c4a994c98d050b2b4b9
diff --git a/libs/graphicsenv/GraphicsEnv.cpp b/libs/graphicsenv/GraphicsEnv.cpp
index 626581c..03e6456 100644
--- a/libs/graphicsenv/GraphicsEnv.cpp
+++ b/libs/graphicsenv/GraphicsEnv.cpp
@@ -639,7 +639,7 @@
 // List of ANGLE features to override (enabled or disable).
 // The list of overrides is loaded and parsed by GpuService.
 void GraphicsEnv::updateAngleFeatureOverrides() {
-    if (!graphicsenv_flags::feature_overrides()) {
+    if (!graphicsenv_flags::angle_feature_overrides()) {
         return;
     }
 
@@ -654,7 +654,7 @@
 
 void GraphicsEnv::getAngleFeatureOverrides(std::vector<const char*>& enabled,
                                            std::vector<const char*>& disabled) {
-    if (!graphicsenv_flags::feature_overrides()) {
+    if (!graphicsenv_flags::angle_feature_overrides()) {
         return;
     }