[ML] [AIOps] Pattern analysis tab in Discover enhancements

Meta issue for follow on tasks for the initial work to add a pattern analysis tab to Discover https://github.com/elastic/kibana/pull/178916

[ ] Replace expanded rows with flyout similar to the existing document viewer in Discover. Suggested here.
[ ] Refactor menu item wrappers which currently reuse an existing discover class for their styles Suggested here.
[ ] Investigate validation which reports 0% contain 3 or more tokens when data appears to contain tokens.
[ ] Fix mobile view as per this comment.
[ ] Investigate the occasional delay when pressing the cancel button
[ ] Add a restart button after cancel has been pressed.
[ ] Fix minor layout issues as per this comment.

elastic / kibana