…hould disable ESQL Tab. (elastic#182816)

## Summary

handles elastic#182798

Recently there was PR : elastic#181616
which does not disable ES|QL tab in timeline even if feature flag is
disabled when :
- User has already created a ESQL Query in timeline and saved the
timeline.

This PR makes sure when below feature flag exists, then `ES|QL` tab will
be definitely disabled even when user has a saved timeline with ES|QL
Query in it.

```yaml
xpack.securitySolution.enableExperimental:
  - timelineEsqlTabDisabled

```

## Desk Testing Guidelines

1. Remove above Feature Flag
2. Go to Timeline and Create a Timeline with ESQL Query
3. Save the timeline.
4. Go To advanced Settings and search for `esql` and disable the
`enableESQL` setting.
5. Go back to the timeline saved in step 3.
6. ✅ Assert that the `ES|QL` tab is still there.
7. ✅ Assert that the `ES|QL` tab is NOT there in a new timeline.
8. Add above feature flag - which disables the esql Tab.
9. Go back to the timeline saved in step 3.
10. ✅ Assert that the `ES|QL` tab is no longer there.
11. ✅ Assert that the `ES|QL` tab is NOT there in a new timeline.

### Checklist

- [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

(cherry picked from commit c43da3e)