Get legacy license logic out of Bazel and replace with a more general framework

Bazel has legacy support for license-checking third party dependencies that has a) never properly worked and b) messed up tasks that have nothing to do with licensing.

Examples:

* https://github.com/bazelbuild/bazel/issues/3639
* https://github.com/bazelbuild/bazel/issues/7194
* https://github.com/bazelbuild/bazel/issues/188
* https://github.com/bazelbuild/bazel/pull/7262
* https://github.com/bazelbuild/bazel/issues/1440
* https://github.com/bazelbuild/bazel/issues/6420

Plans are underway for a replacement (https://github.com/bazelbuild/bazel/issues/7194#issuecomment-460384466, https://github.com/bazelbuild/bazel/issues/188#issuecomment-444271909) which will not need to be directly built into Bazel.

Whatever timeline that replacement happens at, the legacy logic represents a broken API and should be removed for Bazel 1.0.

The issue names no files, tests, or entry points. Start by reviewing the referenced replacement plans, issues, and pull request to identify the legacy license-checking paths; done means removing the broken Bazel-integrated logic without disrupting unrelated tasks.

Written by the indexing model from the issue text.