fix(coderd): workspaceapps: update last_used_at when workspace app reports stats (#11603)

- Adds a new query BatchUpdateLastUsedAt
- Adds calls to BatchUpdateLastUsedAt in app stats handler upon flush
- Passes a stats flush channel to apptest setup scaffolding and updates unit tests to assert modifications to LastUsedAt.

enterprise/coderd/coderdenttest/proxytest.go

@@ -37,6 +37,9 @@ type ProxyOptions struct {
 
 	// ProxyURL is optional
 	ProxyURL *url.URL
+
+	// FlushStats is optional
+	FlushStats chan chan<- struct{}
 }
 
 // NewWorkspaceProxy will configure a wsproxy.Server with the given options.
@@ -113,6 +116,9 @@ func NewWorkspaceProxy(t *testing.T, coderdAPI *coderd.API, owner *codersdk.Clie
 	// Inherit collector options from coderd, but keep the wsproxy reporter.
 	statsCollectorOptions := coderdAPI.Options.WorkspaceAppsStatsCollectorOptions
 	statsCollectorOptions.Reporter = nil
+	if options.FlushStats != nil {
+		statsCollectorOptions.Flush = options.FlushStats
+	}
 
 	wssrv, err := wsproxy.New(ctx, &wsproxy.Options{
 		Logger:            slogtest.Make(t, nil).Leveled(slog.LevelDebug),