This aligns its behaviour better with `nvim_win_close`.

Note that `:hide` is actually incapable of closing the cmdwin, unlike `:close`
and `:quit`, so this is a bit of a difference in behaviour.

Problem: nvim_buf_set_text(), nvim_open_term() and termopen() all change buffer
text, which is forbidden during textlock. Additionally, nvim_open_term() and
termopen() may be used to convert the cmdwin buffer into a terminal buffer,
which is weird.

Solution: Allow nvim_buf_set_text() and nvim_open_term() in the cmdwin, but
disallow nvim_open_term() from converting the cmdwin buffer into a terminal
buffer. termopen() is not allowed in the cmdwin (as it always operates on
curbuf), so just check text_locked().

Also happens to improve the error in #21055: nvim_buf_set_text() was callable
during textlock, but happened to check textlock indirectly via u_save();
however, this caused the error to be overwritten by an unhelpful "Failed to
save undo information" message when msg_list == NULL (e.g: an `<expr>` mapping
invoked outside of do_cmdline()).

Problem: some API functions that check textlock (usually those that can change
curwin or curbuf) can break the cmdwin.

Solution: make FUNC_API_CHECK_TEXTLOCK call text_locked() instead, which already
checks for textlock, cmdwin and `<expr>` status.

Add FUNC_API_TEXTLOCK_ALLOW_CMDWIN to allow such functions to be usable in the
cmdwin if they can work properly there; the opt-in nature of this attribute
should hopefully help mitigate future bugs.

Also fix a regression in #22634 that made functions checking textlock usable in
`<expr>` mappings, and rename FUNC_API_CHECK_TEXTLOCK to FUNC_API_TEXTLOCK.

Problem:    Incsearch not triggered when pasting clipboard register on the
            command line.
Solution:   Also set "literally" when using a clipboard register. (Ken Takata,
            closes vim/vim#12460)

https://github.com/vim/vim/commit/9cf6ab133227ac7e9169941752293bb7178d8e38

Co-authored-by: K.Takata <kentkt@csc.jp>

Co-authored-by: zeertzjq <zeertzjq@outlook.com>
Co-authored-by: famiu <famiuhaque@protonmail.com>

test: replace lfs with luv

luv already pretty much does everything lfs does, so this duplication
of dependencies isn't needed.

Now with try_end() including more exception info, E5500 looks like
redundant information.
Adjust tests for more exception information.

Problem:    Get ml_get error when deleting a line in 'completefunc'. (Yegappan
            Lakshmanan)
Solution:   Lock the text while evaluating 'completefunc'.
https://github.com/vim/vim/commit/ff06f283e3e4b3ec43012dd3b83f8454c98f6639

Fix a mistake in the porting of patch 8.1.0098.
Cherry-pick Test_run_excmd_with_text_locked() from patch 8.2.0270.
Cherry-pick test_gf.vim changes from patch 8.2.0369.
Cherry-pick message change from later patches.

Problem:
Subdirectories like "visual", "insert", "normal" encourage people to
separate *related* tests for no good reason.  Typically the _mode_ is
not the relevant topic of a test (and when it is, _then_ create
an appropriate describe() or it()).

Solution:
- Delete the various `test/functional/<mode>/` subdirectories, move
  their tests to more meaningful topics.
- Rename `…/normal/` to `…/editor/`.
  - Move or merge `…/visual/*` and `…/insert/*` tests into here where
    appropriate.
- Rename `…/eval/` to `…/vimscript/`.
  - Move `…/viml/*` into here also.

* test(reorg): insert/* => editor/mode_insert_spec.lua
* test(reorg): cmdline/* => editor/mode_cmdline_spec.lua
* test(reorg): eval core tests => eval_spec.lua