Synchronize status command between gerrit and gitiles

This is a prepation step for linking JGit as a submodule.
For stamping of JGit artifacts, revision version must be exposed in
workspace status command. Use this opportunity to synchronize status
command between gerrit and gitiles repositories and migrate shell script
to python.

Change-Id: If30c42578396f31beee45998e5f2fa75d69703af

.bazelrc

diff --git a/.bazelrc b/.bazelrc
index dde54fe..52d8749 100644
--- a/.bazelrc
+++ b/.bazelrc
@@ -1,4 +1,4 @@
-build --workspace_status_command=./tools/workspace-status.sh
+build --workspace_status_command="python3 ./tools/workspace_status.py"
 build --repository_cache=~/.gerritcodereview/bazel-cache/repository
 build --experimental_strict_action_env
 build --action_env=PATH