nm-settings-nmcli: show proper valid values of ip-tunnel properties
Summary
Show all valid properties for ip-tunnel.mode, not only 2 examples.
Show constants as values suitable for user input in nmcli. That means showing, for example, "ipip (1)" instead of "IP_TUNNEL_MODE_IPIP (1)".
Checklist
Please read https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/blob/main/CONTRIBUTING.md before opening the merge request. In particular, check that:
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the subject for all commits is concise and explicative -
the message for all commits explains the reason for the change -
the source is properly formatted -
any relevant documentation is up to date -
you have added unit tests if applicable