Problem: - With expanded messages exceeding cfg.msg.cmd.height, entering
the cmdline scrolls to the bottom and expands to the full "cmd"
buffer text height.
- Cursor in the pager is not always at the last message and at
the bottom of the window when appending to the pager.
- unreliable test: messages2_spec: "closed msg window timer removes
empty lines".
Solution: - Achieve separation of the cmdline and message text by moving
messages to the dialog window when entering the cmdline below
expanded messages.
- Set cursor to start of the first message only when first
entering the pager. Use `norm! zb` to position last message
at the bottom of the window (which shouldn't crash anymore
since 911337eb).
- Increase cfg.msg.msg.timeout used in the test file.
b2adfe775d