Migrate `tools/bazel.rc` to `.bazelrc`

Since: [1] Bazel changed the list of resource file locations.
Adapt to that list and move `%workspace%/tools/bazelrc` to
`%workspace%/.bazelrc`.

[1] https://github.com/bazelbuild/bazel/commit/ec83598

Change-Id: I81214ef2593db520c9340e2083446090b0cfa77d