Correctly expose EGL_ANDROID_native_fence_sync to hwui

When we moved off of gui/SyncFeatures for retrieving this extension, we
accidentally didn't include the eglQueryStringImplementationANDROID path
for retrieving extensions. Fortunately this extension is only used for
TextureView synchronization, but we should still use the extension when
available.

Bug: 159921224
Test: Manually inject log statements to verify the extension is
correctly visible.

Change-Id: Idaa872778afc13e86bdea918da8631b4747fe9c1