Add netlink support for bridge port options
sysfs is deprecated and kernel will not add new bridge port options to sysfs. Netlink is a stable API and therefore is the right method to communicate with kernel in order to set the link options.
Please read https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/blob/main/CONTRIBUTING.md before opening the merge request. In particular, check that:
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