feat: Add destroy to workspace provision job (#373)

* ci: Update DataDog GitHub branch to fallback to GITHUB_REF

This was detecting branches, but not our "main" branch before.
Hopefully this fixes it!

* Add basic Terraform Provider

* Rename post files to upload

* Add tests for resources

* Skip instance identity test

* Add tests for ensuring agent get's passed through properly

* Fix linting errors

* Add echo path

* Fix agent authentication

* fix: Convert all jobs to use a common resource and agent type

This enables a consistent API for project import and provisioned resources.

* Add "coder_workspace" data source

* feat: Remove magical parameters from being injected

This is a much cleaner abstraction. Explicitly declaring the user
parameters for each provisioner makes for significantly simpler
testing.

* feat: Add graceful exits to provisionerd

Terraform (or other provisioners) may need to cleanup state, or
cancel actions before exit. This adds the ability to gracefully
exit provisionerd.

* Fix cancel error check

* feat: Add destroy to workspace provision job

This enables the full flow of create/update/delete.

coderd/provisionerdaemons.go

@@ -693,6 +693,8 @@ func convertWorkspaceTransition(transition database.WorkspaceTransition) (sdkpro
 		return sdkproto.WorkspaceTransition_START, nil
 	case database.WorkspaceTransitionStop:
 		return sdkproto.WorkspaceTransition_STOP, nil
+	case database.WorkspaceTransitionDelete:
+		return sdkproto.WorkspaceTransition_DESTROY, nil
 	default:
 		return 0, xerrors.Errorf("unrecognized transition: %q", transition)
 	}