[Discover] [ES|QL] Disables sorting for Document view (elastic#187553)

## Summary

Disables the `@timestamp` sorting for ES|QL Document view. 

The sorting doesnt work currently. I could enable it but this causes 2
problems:

- The fix is here
https://github.com/elastic/kibana/blob/main/packages/kbn-unified-data-table/src/components/data_table.tsx#L962
The timestamp column is a special column for Discover so the
columns.length is 0 here even if the timestamp column is being rendered.
As a result the inMemory is false and the client side sorting doesnt
work. Removing the columns.length fixes it but it makes Discover
significantly slower.
- As the data are not by default sorted by timestamp even if we enable
it client side, it won't be of great help. I think that for the
timestamp column it would be better to enable server side sorting but
this needs discussion

I think that hiding this for now it will fix the confusion and is a good
temporary decision before we decide what to do with sorting in general.

packages/kbn-unified-data-table/src/components/data_table.tsx

@@ -828,6 +828,12 @@ export const UnifiedDataTable = ({
 
   const sorting = useMemo(() => {
     if (isSortEnabled) {
+      // in ES|QL mode, sorting is disabled when in Document view
+      // ideally we want the @timestamp column to be sortable server side
+      // but it needs discussion before moving forward like this
+      if (isPlainRecord && !columns.length) {
+        return undefined;
+      }
       return {
         columns: sortingColumns,
         onSort: onTableSort,
@@ -837,7 +843,7 @@ export const UnifiedDataTable = ({
       columns: sortingColumns,
       onSort: () => {},
     };
-  }, [isSortEnabled, sortingColumns, onTableSort]);
+  }, [isSortEnabled, sortingColumns, isPlainRecord, columns.length, onTableSort]);
 
   const canSetExpandedDoc = Boolean(setExpandedDoc && !!renderDocumentView);
 

test/functional/apps/discover/esql/_esql_view.ts

@@ -85,7 +85,8 @@ export default function ({ getService, getPageObjects }: FtrProviderContext) {
         expect(await testSubjects.exists('discoverQueryHits')).to.be(true);
         expect(await testSubjects.exists('discoverAlertsButton')).to.be(true);
         expect(await testSubjects.exists('shareTopNavButton')).to.be(true);
-        expect(await testSubjects.exists('dataGridColumnSortingButton')).to.be(true);
+        // we don't sort for the Document view
+        expect(await testSubjects.exists('dataGridColumnSortingButton')).to.be(false);
         expect(await testSubjects.exists('docTableExpandToggleColumn')).to.be(true);
         expect(await testSubjects.exists('fieldListFiltersFieldTypeFilterToggle')).to.be(true);
         await testSubjects.click('field-@message-showDetails');

x-pack/test_serverless/functional/test_suites/common/discover/esql/_esql_view.ts

@@ -84,7 +84,7 @@ export default function ({ getService, getPageObjects }: FtrProviderContext) {
         await testSubjects.existOrFail('discoverQueryHits');
         await testSubjects.existOrFail('discoverAlertsButton');
         await testSubjects.existOrFail('shareTopNavButton');
-        await testSubjects.existOrFail('dataGridColumnSortingButton');
+        await testSubjects.missingOrFail('dataGridColumnSortingButton');
         await testSubjects.existOrFail('docTableExpandToggleColumn');
         await testSubjects.existOrFail('fieldListFiltersFieldTypeFilterToggle');
         await testSubjects.click('field-@message-showDetails');