Add properties for vulkan apex

ro.vulkan.apex property is added to tell which APEX provides vulkan
driver.

Bug: 205618237
Test: CtsGraphicsTestCases
Change-Id: Icdf6ee5ede16c08405f48d736ed38ad4117d8e2d
diff --git a/private/property_contexts b/private/property_contexts
index 56ccb40..f4e6ff4 100644
--- a/private/property_contexts
+++ b/private/property_contexts
@@ -1430,6 +1430,8 @@
 
 ro.cpuvulkan.version u:object_r:graphics_config_prop:s0 exact int
 
+ro.vulkan.apex          u:object_r:graphics_config_prop:s0 exact string
+
 # surfaceflinger-settable
 graphics.display.kernel_idle_timer.enabled u:object_r:surfaceflinger_display_prop:s0 exact bool