Define ro.vendor.api_level

ro.vendor.api_level will have the api_level that the vendor images
are required to implement based on the various api level properties.

Bug: 200258600
Test: getprop ro.vendor.api_level
Change-Id: Ie4f71ef920f03bdbc0a904936c26f092429fcd7f
diff --git a/private/property_contexts b/private/property_contexts
index 6915759..879b7f9 100644
--- a/private/property_contexts
+++ b/private/property_contexts
@@ -881,6 +881,7 @@
 # GRF property for the first api level of the vendor partition
 ro.board.first_api_level u:object_r:build_vendor_prop:s0 exact int
 ro.board.api_level       u:object_r:build_vendor_prop:s0 exact int
+ro.vendor.api_level      u:object_r:build_vendor_prop:s0 exact int
 
 # Boot image build props set by /{second_stage_resources/,}boot/etc/build.prop
 ro.bootimage.build.date                        u:object_r:build_bootimage_prop:s0 exact string