[Management] Test and address multi-cluster setups with new index pattern page

[chrisronline]

#13454 brought in a new UI for index pattern creation, but it also does a *:* search to start the page. This might timeout for users with multi clusters spread out across the world. We should handle this properly as the page currently breaks if that request times out.

Some ideas:

• Handle the timeout error properly
• Maybe do a single cluster search initially, then prompt the user for cross cluster searching