Add programs.ssh.settings as a freeform DAG for OpenSSH client configuration blocks. Render Host and Match blocks directly from the new settings option while preserving ordering support.
Render known ssh_config comma-list directives from Nix lists as single comma-separated lines and known space-list directives as single whitespace-separated lines. This keeps directives like KexAlgorithms, Ciphers, MACs, HostKeyAlgorithms, ProxyJump, SendEnv, GlobalKnownHostsFile, and PermitRemoteOpen from being emitted as duplicate directives where OpenSSH may only use the first value.
Migrate legacy matchBlocks into settings, keep root SSH option redirects pointed at the new option names, and hide the deprecated matchBlocks option from generated docs.
Update SSH tests, docs references, and news coverage for the new option.
The `optionsDocBook` function is deprecated in nixpkgs since
nixos-23.11. This commit updates the manual and manpages to
use commonmark formatted documentation instead of the deprecated
docbook format.
