Kibana version:
7.7

Elasticsearch version:
7.7

Server OS version:
OpenSUSE 15.1

Browser version:
Chrome 83

Browser OS version:
Win10 x64 May 2020 update

Original install method (e.g. download page, yum, from source, etc.):
zypper

Describe the bug:
Discover UI uses so much CPU, it freezes for multiple seconds and sometimes uses 100%+ CPU non-stop.

Steps to reproduce:

1. Load Discover with some data.
2. Try to enable some columns, move them around, or in our case simply hover on Selected Fields without even selecting them.
3. Observe the CPU for the tab spike to 100%+ and the whole UI become very laggy. Help you lord if you do this after refreshing the data a few times or changing up some queries. I frequently have to close and reopen the tab just to get it to respond again and not be a laggy mess. Just moving the mouse around the empty area of the screen starts using 20-50% CPU for the tab.

Expected behavior:
Decent performance without page hangs.

Screenshots (if relevant):

Errors in browser console (if relevant):

Provide logs and/or server output (if relevant):

Any additional context: