Add accept-new as valid option for ssh_config host key checking (#8257)
* Add accept-new as valid option for host key checking
* Add changelog fragment for #8257
* Apply suggestions from code review
Co-authored-by: Felix Fontein <felix@fontein.de>
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Co-authored-by: Felix Fontein <felix@fontein.de>
(cherry picked from commit af1c5dd785)
Co-authored-by: Maxopoly <max@dermax.org>