Add information about Module Metadata Version into bugreport header

* In case device supports mainline, the following line will be added
  to the header of a bugreport:
  Module Metadata version: <version-of-module-metadata-package>
* Otherwise this line will be omitted.

Test: adb bugreport /tmp/bugreports
Bug: 131774400
Change-Id: I03f8c10039381cf788ff353893c82a9beaaaaca8