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: I3d2c05691b757684ba8f816cf2669c754dd77888
(cherry picked from commit b31596bb73cc8a67481ba3439f44384341bd15e4)