Discover - Field names under "available fields" are truncated, should have a way to display full field names

[jbehrends]

We are currently indexing large JSON objects. This means that some of our field names are quite large and end up being up to 40 or more characters long. On the "Discover" screen, the left bar which displays "available fields", a majority of our fields are truncated at about 27 or 28 characters. The only way to to see the full field name is to mouse over each entry which is slow and time consuming. There should be a way to resize/drag this window/frame to the right allowing the user to see full field names.

[elasticmachine]

Pinging @elastic/kibana-app

[Bargs]

Duplicate of #4881

Since you mentioned you're dealing with large JSON objects, the "short dots" advanced setting might help in your case.