Automatic merge from submit-queue

Speed up dockerized builds

This PR speeds up dockerized builds.  First, we make sure that we are as incremental as possible.  The bigger change is that now we use rsync to move sources into the container and get data back out.

To do yet:
* [x] Add a random password to rsync.  This is 128bit MD4, but it is better than nothing.
* [x] Lock down rsync to only come from the host.
* [x] Deal with remote docker engines -- this should be necessary for docker-machine on the mac.
* [x] Allow users to specify the port for the rsync daemon.  Perhaps randomize this or let docker pick an ephemeral port and detect the port?
* [x] Copy back generated files so that users can check them in.  This is done for `zz_generated.*` files generated by `make generated_files` 
  * [x] This should include generated proto files so that we can remove the hack-o-rama that is `hack/hack/update-*-dockerized.sh` 
* [x] Start "versioning" the build container and the data container so that the CI system doesn't have to be manually kicked.
* [x] Get some benchmarks to qualify how much faster.

This replaces #28518 and is related to #30600.

cc @thockin @spxtr @david-mcmahon @MHBauer 

Benchmarks by running `make clean ; sync ; time bash -xc 'time build/make-build-image.sh ; time sync ; time build/run.sh make ; time sync; time build/run.sh make'` on a GCE n1-standard-8 with PD-SSD.

| setup | build image | sync | first build | sync | second build | total |
|-------|-------------|----- |----------|------|--------------|------|
| baseline | 0m11.420s | 0m0.812s | 7m2.353s | 0m42.380s | 7m8.381s | 15m5.348s |
| this pr | 0m10.977s | 0m15.168s | 7m31.096s | 1m55.692s | 0m16.514s | 10m9.449s |