LibUp

We need a utility/tool to semi-automatically manage upgrades of libraries and other developer dependencies for dozens/hundreds of repos instead of developers (aka Legoktm) running scripts on their laptops.

Basic requirements: Nice-to-haves:
 * Does not run under Legoktm's gerrit account
 * Pick a few canary repositories to do the upgrade first, then submit patches to bulk upgrade the rest
 * Ability to specifically pick what library to upgrade
 * All submitted patches use the " " topic
 * Web interface for everything!!11
 * Discovers new repositories immediately instead of a hardcoded list

Cool features:
 * Know which repos are going to fail the upgrade beforehand

Implementation notes:
 * labs project requested: T116697
 * Code in gerrit labs/libraryupgrader
 * Uses docker for all actions, so everything is sandboxed and easy to clean up