[ML] [META] Log pattern analysis improvements

[jgowdyelastic]

Meta issue to track requested improvements to the Log Pattern Analysis page.

• Validate field selected for analysis [ML] Adds validation of field selected for log pattern analysis #162319
• Store all page options in the URL for reloading after a page refresh
  • Field selection [ML] Adds validation of field selected for log pattern analysis #162319
  • Date range
  • Search bar settings
• Drag to select time range in main chart
• Consolidate aiops to Discover link generation
• The Discover links should add any query / filter from the search bar to the query from the pattern being explored
• Refactor DatePickerWrapper to improve places where it is used as a hook dependency [ML] Log pattern analysis UI #139005 (comment)
• Sticky document count chart, so it remains visible when scrolling and hovering / selecting rows at the bottom of the table
• Improve empty state UX - for example by including information on how to use the view
• Improve 'No results' messaging, such as when the analysis is run over a time range when there are no docs.

[elasticmachine]

Pinging @elastic/ml-ui (:ml)