Add pre and post deploy steps to Cloud Deploy delivery pipeline

[jicelhay]

This also introduces some QoL changes to the pipeline:

• It fixes the image tagging step and adds an automation rule so the canary steps don't need manual approval.
• The verify schema step in crash is skipped, since the db in this env can be manually modified to test local changes.
• It sets the number of replicas in partial deployments of backend and console = 1, otherwise they would be bigger than the stable deployments.

This change is 

[gbrodman]

@gbrodman reviewed 5 files and all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on gbrodman).