Define vendor side property "ro.camerax.extensions.enabled"

Add "ro.camerax.extensions.enabled" vendor-specific property.
Allow public apps to read this property.

Bug: 171572972
Test: Camera CTS
Change-Id: Id5fadedff6baaaebe5306100c2a054e537aa61ed
diff --git a/private/property_contexts b/private/property_contexts
index c7d6743..34efaac 100644
--- a/private/property_contexts
+++ b/private/property_contexts
@@ -323,6 +323,8 @@
 ro.camera.notify_nfc    u:object_r:camera_config_prop:s0 exact bool
 ro.camera.enableLazyHal u:object_r:camera_config_prop:s0 exact bool
 
+ro.camerax.extensions.enabled u:object_r:camerax_extensions_prop:s0 exact bool
+
 # Should always_debuggable be bool? It's checked against the string "1".
 dalvik.vm.always_debuggable                   u:object_r:dalvik_config_prop:s0 exact int
 dalvik.vm.appimageformat                      u:object_r:dalvik_config_prop:s0 exact string