Merge branch 'stable-3.1' into stable-3.2

* stable-3.1:
  Introduce a configuration to define time lapse for rate limiter
  Upgrade bazlets to latest stable-3.1 to build with 3.1.12 API
  Upgrade bazlets to latest stable-3.0 to build with 3.0.15 API
  Upgrade bazlets to latest stable-2.16 to build with 2.16.26 API
  Upgrade bazlets to latest stable-2.16 to build with 2.16.23 API

Conflict resolution for WORKSPACE is to keep the original bazlets
version.

Change-Id: I5715b80e809117dada62f1d1bc4dab4d4712d038