Merge branch 'stable-3.1' into master

* stable-3.1:
  Bump Bazel version to 3.7.0
  Upgrade bazlets to latest stable-3.0 to build with 3.0.13 API

Change-Id: Ia73ad200fb9cfbf3913d32abe65a88fe9a59d967

.bazelversion

diff --git a/.bazelversion b/.bazelversion
index 1545d96..7c69a55 100644
--- a/.bazelversion
+++ b/.bazelversion
@@ -1 +1 @@
-3.5.0
+3.7.0