[ES|QL] fixes getIndexPatternFromESQLQuery for comma separated indices (#169562)

## Summary

Comma separated source indices work as expected with ES|QL query, but
`getIndexPatternFromESQLQuery` does not parses it correctly. This small
PR is an attempt to fix this behavior

### Before

```ts
      const idxPattern7 = getIndexPatternFromESQLQuery('from foo-1, foo-2 | limit 2');
      expect(idxPattern7).toBe('foo-1,');
```

### After
```ts
      const idxPattern7 = getIndexPatternFromESQLQuery('from foo-1, foo-2 | limit 2');
      expect(idxPattern7).toBe('foo-1, foo-2');
```

### Checklist

Delete any items that are not applicable to this PR.

- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios

Co-authored-by: Stratoula Kalafateli <efstratia.kalafateli@elastic.co>

packages/kbn-es-query/src/es_query/es_aggregate_query.test.ts

@@ -101,6 +101,18 @@ describe('sql query helpers', () => {
 
       const idxPattern5 = getIndexPatternFromESQLQuery('from foo | limit 2');
       expect(idxPattern5).toBe('foo');
+
+      const idxPattern6 = getIndexPatternFromESQLQuery('from foo-1,foo-2 | limit 2');
+      expect(idxPattern6).toBe('foo-1,foo-2');
+
+      const idxPattern7 = getIndexPatternFromESQLQuery('from foo-1, foo-2 | limit 2');
+      expect(idxPattern7).toBe('foo-1, foo-2');
+
+      const idxPattern8 = getIndexPatternFromESQLQuery('FROM foo-1,  foo-2');
+      expect(idxPattern8).toBe('foo-1,  foo-2');
+
+      const idxPattern9 = getIndexPatternFromESQLQuery('FROM foo-1, foo-2 [metadata _id]');
+      expect(idxPattern9).toBe('foo-1, foo-2');
     });
   });
 });

packages/kbn-es-query/src/es_query/es_aggregate_query.ts

@@ -59,10 +59,10 @@ export function getIndexPatternFromESQLQuery(esql?: string): string {
   }
   const parsedString = esql?.replaceAll('`', '');
   // case insensitive match for the index pattern
-  const regex = new RegExp(/FROM\s+([\w*-.!@$^()~;]+)/, 'i');
+  const regex = new RegExp(/FROM\s+([\w*-.!@$^()~;\s]+)/, 'i');
   const matches = parsedString?.match(regex);
   if (matches) {
-    return matches[1];
+    return matches[1]?.trim();
   }
   return '';
 }