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/databasefake/databasefake.go

@@ -325,6 +325,20 @@ func (q *fakeQuerier) GetWorkspaceByOwnerIDAndName(_ context.Context, arg databa
 	return database.Workspace{}, sql.ErrNoRows
 }
 
+func (q *fakeQuerier) GetWorkspacesAutostartAutostop(_ context.Context) ([]database.Workspace, error) {
+	q.mutex.RLock()
+	defer q.mutex.RUnlock()
+	workspaces := make([]database.Workspace, 0)
+	for _, ws := range q.workspaces {
+		if ws.AutostartSchedule.String != "" {
+			workspaces = append(workspaces, ws)
+		} else if ws.AutostopSchedule.String != "" {
+			workspaces = append(workspaces, ws)
+		}
+	}
+	return workspaces, nil
+}
+
 func (q *fakeQuerier) GetWorkspaceOwnerCountsByTemplateIDs(_ context.Context, templateIDs []uuid.UUID) ([]database.GetWorkspaceOwnerCountsByTemplateIDsRow, error) {
 	q.mutex.RLock()
 	defer q.mutex.RUnlock()