patch 9.1.1872: Cmdline history not updated when mapping <Up> and <CR>

patch 9.1.1872: Cmdline history not updated when mapping <Up> and <CR>

Problem:  Cmdline history not updated when mapping both <Up> and <CR>.
Solution: Consider the command typed when in Cmdline mode and there is
          no pending input (zeertzjq).

Although the existing behavior technically does match documentation, the
"completely come from mappings" part is a bit ambiguous, because one may
argue that the command doesn't completely come from mappings as long as
the user has typed a key in Cmdline mode.  I'm not entirely sure if this
change will cause problems, but it seems unlikely.

fixes: #2771
related: neovim/neovim#36256
closes: #18607

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>