Problem: Newlines intended to write messages below the cmdline or to
mark the start of a new message on message grid are emitted
through ext_messages. This results in unnecessary newlines for
a UI that has decoupled its message area from the cmdline.
msg_col is set directly in some places which is not transmitted
to msg_show events.
Various missing message kind for list commands.
Trailing newlines on various list commands.
Solution: Only emit such newlines without ext_messages enabled.
Use msg_advance() instead of setting msg_col directly.
Assign them the "list_cmd" kind.
Ensure no trailing newline is printed.
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