[Discover] Refresh fields when entering Discover (#160195)

- Closes #156556
- Probably also addresses
#157239

## Summary

This PR allows to refresh fields list when revisiting Discover page.

## For testing

1. Open discover
2. In a separate tab open Dev Tools and create documents which include
new field names
3. Press "Refresh" in the unified search bar on Discover and notice that
new fields appear under Unmapped section
4. Navigate to another Kibana app (for example Home page)
5. Navigate back to Discover and notice that new fields are now under
Available section and have a proper icon.

src/plugins/discover/public/application/main/utils/resolve_data_view.ts

@@ -70,7 +70,7 @@ export async function loadDataView({
   let fetchedDataView: DataView | null = null;
   // try to fetch adhoc data view first
   try {
-    fetchedDataView = fetchId ? await dataViews.get(fetchId, false) : null;
+    fetchedDataView = fetchId ? await dataViews.get(fetchId, false, true) : null;
     if (fetchedDataView && !fetchedDataView.isPersisted()) {
       return {
         list: dataViewList || [],
@@ -88,7 +88,10 @@ export async function loadDataView({
   let defaultDataView: DataView | null = null;
   if (!fetchedDataView) {
     try {
-      defaultDataView = await dataViews.getDefaultDataView({ displayErrors: false });
+      defaultDataView = await dataViews.getDefaultDataView({
+        displayErrors: false,
+        refreshFields: true,
+      });
     } catch (e) {
       //
     }