Autopromote deployments using API

[jordiori]

Related to #111

Make the deployment auto-promote behaviour equivalent to the CLI.

Deployments now call the API with auto_promote=true instead of relying on polling and calling /set-live + DELETE previous. Adds --wait / --no-wait and --auto / --no-auto flags to tb deploy (both default true), matching the CLI.

[eclbg]

Let's think about how this might affect users who've been using previous version. I see that SDK users keep 2 active deployments, with the latest one as live. And I wonder if when we merge this they'll get the "deployment already in progress" error.

[jordiori]

Let's think about how this might affect users who've been using previous version. I see that SDK users keep 2 active deployments, with the latest one as live. And I wonder if when we merge this they'll get the "deployment already in progress" error.

I think that was the old behavior but it was changed here. This new PR just changes that it will be done by the backend directly when auto-promoting instead of relying on polling and deleting from the SDK.

For users that may still have 2 active deployments, we still have this check that auto-deletes any "stale" deployment before running a new one.

[eclbg]

LGTM, Thanks Jordi