Check vendor_property_contexts namespaces

For devices launching with Android Q or later, vendor_property_contexts
and odm_property_contexts should only contain vendor and odm properties.
This checks property_contexts files in build time.

To temporarily disable this check, users can set
BUILD_BROKEN_VENDOR_PROPERTY_NAMESPACE := true in BoardConfig.mk. But
VTS is still enforced, so users will have to fix the violations anyway.

Bug: 175526482
Test: m vendor_property_contexts after making violations
Change-Id: I99d6fff9033d78e1d276eed2682a2719dab84ae2
diff --git a/tests/Android.bp b/tests/Android.bp
index 5925fc2..6a86188 100644
--- a/tests/Android.bp
+++ b/tests/Android.bp
@@ -87,3 +87,8 @@
     ],
     defaults: ["py2_only"],
 }
+
+python_binary_host {
+    name: "check_prop_prefix",
+    srcs: ["check_prop_prefix.py"],
+}