It adds standard JSON module with json.encode(...), json.decode(...)
and json.indent(...).

R=iannucci@chromium.org
BUG=1130833

Change-Id: I0b217fdcd062cb5102991c506bc431c9eafe9e95
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2432110Reviewed-by: Scott Lee <ddoman@chromium.org>
Commit-Queue: Vadim Shtayura <vadimsh@chromium.org>