feat: add lifecycle.Executor to manage autostart and autostop (#1183)

This PR adds a package lifecycle and an Executor implementation that attempts to schedule a build of workspaces with autostart configured.

- lifecycle.Executor takes a chan time.Time in its constructor (e.g. time.Tick(time.Minute))
- Whenever a value is received from this channel, it executes one iteration of looping through the workspaces and triggering lifecycle operations.
- When the context passed to the executor is Done, it exits.
- Only workspaces that meet the following criteria will have a lifecycle operation applied to them:
  - Workspace has a valid and non-empty autostart or autostop schedule (either)
  - Workspace's last build was successful
- The following transitions will be applied depending on the current workspace state:
  - If the workspace is currently running, it will be stopped.
  - If the workspace is currently stopped, it will be started.
  - Otherwise, nothing will be done.
- Workspace builds will be created with the same parameters and template version as the last successful build (for example, template version)

coderd/database/queries/workspaces.sql

@@ -14,6 +14,20 @@ SELECT * FROM workspaces WHERE organization_id = $1 AND deleted = $2;
 -- name: GetWorkspacesByOrganizationIDs :many
 SELECT * FROM workspaces WHERE organization_id = ANY(@ids :: uuid [ ]) AND deleted = @deleted;
 
+-- name: GetWorkspacesAutostartAutostop :many
+SELECT
+	*
+FROM
+	workspaces
+WHERE
+	deleted = false
+AND
+(
+	autostart_schedule <> ''
+	OR
+	autostop_schedule <> ''
+);
+
 -- name: GetWorkspacesByTemplateID :many
 SELECT
 	*