[8.14](backport #3939) Add docs about the Hosts metrics tab

[mergify]

Closes #3788.

Also adds a couple other additional (minor) changes:

• Cleans up some outdated text from other subtle UI changes.
• Moves the screenshots about host details tabs to appear after the text that explains the tab. Why? Users looking at the UI probably don't need the screenshot and would prefer to see text. Other users (who are maybe trying to figure out what is possible) will still see the screenshot but it won't interfere with the users ability to scan and find info.
• Cropped out the search bar in some of the screen captures. Why? Having inconsistent timestamps at the top of each screenshot looked weird plus didn't add a lot since the search field is not unique to each screen. Note that I didn't retake all the screenshots...just cropped them.

[github-actions]

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