docs: Add proxy settings (#17797)

I'm not sure if I placed `Network Proxy` in the correct position. What I
noticed is that the first half of the documentation seems to be
organized alphabetically, but the second half is not. I tried to
position `Network Proxy` in a spot that seemed reasonable while
maintaining alphabetical order. If there's a better suggestion, I'd be
happy to make adjustments.

Release Notes:

- N/A

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Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>