[8.17] [Dashboard] Fix controls being overwritten on navigation (#217596)

Closes https://github.com/elastic/kibana/issues/208330

## Summary

Consider how we set `restoredRuntimeState` for controls in
`initializeDashboard`:


ce91dea75c/src/plugins/dashboard/public/dashboard_container/embeddable/create/create_dashboard.ts (L439-L445)

Now, consider the following scenario:

1. We have two dashboards - dashboard B has unsaved changes to its
control group, and dashboard A does not
2. We start in dashboard B and, since it has unsaved control changes,
`restoredRuntimeState[PANELS_CONTROL_GROUP_KEY]` (in
`DashboardContainer`) is populated with these changes
3. We navigate to Dashboard A via the `navigateToDashboard` method,
which calls `initializeDashboard`
4. In `initializeDashboard`, `overrideInput` does **not** have control
group state for dashboard A (since it does not have unsaved control
changes) - so, we skip calling `setRuntimeStateForChild` for dashboard A
5. This means that `DashboardContainer` still has
`restoredRuntimeState[PANELS_CONTROL_GROUP_KEY]` equal to the changes
from dashboard B, which results in Dashboard A's control group getting
overwritten with `restoredRuntimeState[PANELS_CONTROL_GROUP_KEY]` 🔥

If we clear `restoredRuntimeState` in `navigateToDashboard`, this is no
longer an issue - we will now start from a blank slate on navigation,
which is the desired behaviour.


**Before**


https://github.com/user-attachments/assets/d04fa41f-2603-4b64-963d-b59c6be6fa14

**After**


https://github.com/user-attachments/assets/ce42c204-4ed0-4c44-8c15-c2f49a60131b

src/plugins/dashboard/public/dashboard_container/embeddable/dashboard_container.tsx

@@ -752,6 +752,7 @@ export class DashboardContainer
     newSavedObjectId?: string,
     newCreationOptions?: Partial<DashboardCreationOptions>
   ) => {
+    this.restoredRuntimeState = undefined; // restored runtime state will be set in `initializeDashboard`, if necessary
     this.integrationSubscriptions.unsubscribe();
     this.integrationSubscriptions = new Subscription();
     this.stopSyncingWithUnifiedSearch?.();