* We are interested mostly in the conversion the `default_applicable_licenses`
attribute, as `default_visibility` cannot be handled until every module's
`visibility` is handled.
* Several referenced license modules had to be manually enabled for
conversion, and likewise a few trivial Android.bp containing only
package and license modules.
* As Bazel allows only a single `package` rule, the package rules in a
manually converted BUILD.bazel files were removed (in
external/protobuf and prebuilts/clang/host/linux-x86 trees).
* The converted package rule is emitted before the `load` statements per
Bazel documentation.
Bug: 190817312
Test: treehugger
Change-Id: If8bf6fee1580177de3bb402923615bcd48923ed2
