Baseline: a25dea6096a1a1965ffe8ce023b5121ec4d18422

Important changes:

  - Starlark test rules can use the new inherited_environment
    parameter of testing.TestEnvironment to specify environment
    variables
    whose values should be inherited from the shell environment.

This release contains contributions from many people at Google, as well as Benjamin Lee, Benjamin Peterson, Fabian Meumertzheim, Mikhail Balabin, Ted Kaplan, Zhongpeng Lin.