Before calling "attach" a screen object is just a dummy container for
(row, col) values whose purpose is to be sent as part of the "attach"
function call anyway.

Just create the screen in an attached state directly. Keep the complete
(row, col, options) config together. It is still completely valid to
later detach and re-attach as needed, including to another session.

In the api_info() output:

    :new|put =map(filter(api_info().functions, '!has_key(v:val,''deprecated_since'')'), 'v:val')
    ...

    {'return_type': 'ArrayOf(Integer, 2)', 'name': 'nvim_win_get_position', 'method': v:true, 'parameters': [['Window', 'window']], 'since': 1}

The `ArrayOf(Integer, 2)` return type didn't break clients when we added
it, which is evidence that clients don't use the `return_type` field,
thus renaming Dictionary => Dict in api_info() is not (in practice)
a breaking change.

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.

Work on https://github.com/neovim/neovim/issues/27004.

Problem:    Dialog for file changed outside of Vim not tested.
Solution:   Add a test.  Move FileChangedShell test.  Add 'L' flag to
            feedkeys().

https://github.com/vim/vim/commit/5e66b42aae7c67a3ef67617d4bd43052ac2b73ce

Co-authored-by: Bram Moolenaar <Bram@vim.org>

Followup to 07a7c0ec