[kots] Revise help text on the KOTS config page and add links to docs where applicable

[corneliusludmann]

• [x] this internal feedback about the certificate issuer name
• [x] This internal feedback on naming of the SSH option
• [ ] Feedback on container registry wording
• [ ] Go through rest of the UI wording and ensure consistency, readability and linking to docs

[corneliusludmann]

Comment from @csweichel:

I was tripped up by Container registry server and would not have known how to proceed. The description does not tell me what to do but is too vague (depending on your provider should read if you're on GCP this is gcr.io, if you're on XXX this YYY). Also, renaming the field to Container Registry Host might help.

(internal)

[stale[bot]]

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