Support version controlling environments

[lukehoban]

Today, environments are stored and versioning within Pulumi Cloud. We know there are cases where users would like to be able to author and version their environments via source-controlled code files.

There are two options we are exploring for this:

1. Enabling the Pulumi Cloud Pulumi Provider to define and manage the desired state of Environments via a Pulumi IaC program. This would offer a way to write code (in Pulumi IaC) to manage the lifecycle of environments across an organization (and to detect and manage drift via pulumi refresh).
2. Providing a mode where environments are authored locally (in source controlled Git repo), and pushed up to Pulumi ESC as part of a "deployment" process of some sort directly.

We may ultimately want/need to provide both of these.

### Tasks

[joeduffy]

Am going to guess most users would expect/want something more like 2 (although tbh I expect most people to assume “code” is source of truth). It will be interesting to get feedback before deciding.

[komalali]

Related issue for 1 in pulumiservice provider repo: https://github.com/pulumi/pulumi-pulumiservice/issues/179

[grantjoy]

Any progress on this?

[komalali]

We've released ESC versioning! https://www.pulumi.com/blog/esc-versioning-launch/