gplay tracks (+ availability + testers)

Shared conventions are in gplay-cli-usage; shipping builds onto tracks is gplay-release-flow.

Inspect tracks

gplay tracks list --package com.example.app          # every track on the app
gplay tracks view --track production                 # one track's full state

Create a closed track

gplay tracks create qa-team
gplay tracks create qa-team --if-exists skip     # idempotent: prints the existing track, commits nothing