Check "overwrite.cli.url" if HPB is enabled

[fancycode]

As these errors are triggered by a cron job, make sure that overwrite.cli.url matches the backend configuration in the signaling server. Right now it's http://xxx but should probably be https://xxx.

Originally posted by @fancycode in #14822

Errors like this are reported from time to time (also from HPB service customers), so it would be nice if this could be verified in the setup check and reported to the administrator if the setting is missing / incorrect.

[nickvergessen]

Should be done in the server in general:

• feat(setupcheck): Check several config values to be valid URLs (and more) server#45382

Also there is a check for the domain when accessing via the web, maybe that needs sharpening to yield when it's not https while the page is accessed with https

[fancycode]

That PR only checks for syntactially correct values but for example doesn't check that overwrite.cli.url is actually configured and matches the URL the user is accessing the page through.

Did some more searching and found nextcloud/server#42796 which seems to do the correct check. However incorrect URLs are reported as suggestion with SetupResult::success, so it's not visible in the admin overview in the web but only through occ setupchecks and in green color just like other successfull checks.

Should I report it at the server repository or should the setting be checked separately in Talk where the correct value is more important (causes problems with the HPB if the URL is not setup correctly)?