Configure WV HAL APEX to be updatable

- add "supportRebootless" to apex_manifest.json
- add <allowed-vendor-apex> sysconfig
- add "on property:apex.com.google.android.widevine.ready=true" to .rc

Now, we can test `adb install` new version of the APEX and see the
service is restarted from the new version.

Note that this doesn't mean that DRM Framework works fine with the
update.

Bug: 248192031
Test: adb install --force-non-staged \
   -i com.android.vending \
   $OUT/vendor/com.google.android.widevine.apex
Change-Id: I7c41b224f0bb55742c0023c23196bba4a09e555f

libwvdrmengine/apex/allowlist_com.google.android.widevine.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<!--
+ This XML file declares the vendor apex package names eligible for installation.
+-->
+
+<config>
+<allowed-vendor-apex package="com.google.android.widevine" installerPackage="com.android.vending" />
+</config>