Specifically, functions that are run in the context of the test runner
are put in module `test/testutil.lua` while the functions that are run
in the context of the test session are put in
`test/functional/testnvim.lua`.
Closes https://github.com/neovim/neovim/issues/27004.
Let :wincmd command accept a count like what its documentation suggests.
Previously it could only accept a range, which led to some ambiguity on
which attribute should be used when executing :wincmd using nvim_cmd.
Closes#19662.
Also fix a typo in a related Vim test:
vim-patch:9.0.0223: typo in diffmode test
Problem: Typo in diffmode test.
Solution: Fix the typo. (closesvim/vim#10932)
5fd6ab820b