Merge branch 'stable-3.1'
* stable-3.1:
Bump Bazel version to 2.2.0
Bump required Bazel version to 2.1.0
Upgrade bazlets to latest stable-2.16 to build with 2.16.16 API
Documentation: Remove bazel issue
Documentation: Refactor to match other plugin documentation
Documentation: Add missing alternative for plugin in-tree testing
Upgrade bazlets to latest stable-2.16
Upgrade bazlets to latest stable-2.16
Upgrade bazlets to latest stable-2.15
Upgrade bazlets to latest stable-2.14
Change-Id: I0f0e7e4f918b4d7f0fa1af2024a050bdea658a67