Migrate (i.e. move) `tools/bazel.rc` to `.bazelrc`

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

Commit fe4b901 in stable-2.14 should have been merged up, rather than
needing this change, but was not (either not automatically or ended up
being unknowingly discarded).

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

Change-Id: I4f2ab38d7382a03450b9c2980d151c733c00ef34

.bazelrc

diff --git a/tools/bazel.rc b/.bazelrc
similarity index 100%
rename from tools/bazel.rc
rename to .bazelrc