* Check dependencies' open-source licenses
Use jk1/Gradle-License-Report to verify that all
dependencies have open-source licenses.
Note that the following dependencies are not checked:
Dependencies of official Gradle plugins
Dependencies declared in buildscript block
Dependencies of jk1/Gradle-License-Report itself
* Refactor the license check to be a generic presubmit check
This includes all of the old presubmits that were in our METADATA file
that are still valid.
* Responses to CR
Added docstrings, refactored the file finder, changed variable names,
and formatted the file
* More respones to CR
