Change Data Entry Flow loading step description logic + cleanups (#9558)

* Change Data Entry Flow loading step description logic + cleanups

Fixes #6251

* Lint

* Address comment

src/dialogs/config-flow/show-dialog-data-entry-flow.ts

@@ -79,8 +79,21 @@ export interface FlowConfig {
     hass: HomeAssistant,
     step: DataEntryFlowStepProgress
   ): TemplateResult | "";
+
+  renderLoadingDescription(
+    hass: HomeAssistant,
+    loadingReason: LoadingReason,
+    handler?: string,
+    step?: DataEntryFlowStep | null
+  ): string;
 }
 
+export type LoadingReason =
+  | "loading_handlers"
+  | "loading_flow"
+  | "loading_step"
+  | "loading_devices_areas";
+
 export interface DataEntryFlowDialogParams {
   startFlowHandler?: string;
   continueFlowId?: string;