Baseline: 7e538803

Cherry picks:

   + fa6b1b7e:
     Reverse a RAM regression introduced by
     https://github.com/bazelbuild/bazel/commit/7e538803d775929beb3c9a
     f1cd2e87667d373bbe

Important changes:

  - The new
    `--@bazel_tools//tools/test:incompatible_use_default_test_toolchai
    n` flag can be used to have test actions select an execution
    platform that has all the constraints provided by the target
    platform instead of always selecting the first available
    execution platform. This supersedes the
    `--use_target_platform_for_tests` flag.
  - `--experimental_downloader_config` is now no longer experimental,
    and has been renamed to `--downloader_config`. The old flag name
    can still be used.

This release contains contributions from many people at Google, as well as Benjamin Peterson, Fabian Meumertzheim, Kevin Bernal, Lszl Csomor, tfrench.