Co-authored-by: zeertzjq <zeertzjq@outlook.com>
Co-authored-by: notomo <notomo.motono@gmail.com>

`:lua vim.ls<tab>` would list `lsp` twice.

Problem:
Since right-click can now show a popup menu, we can provide messaging to
guide users who expect 'mouse' to be disabled by default. So 'mouse' can
now be enabled by default.

Solution:
Do it.
Closes #15521

* reformat Lua runtime to make lint CI pass
* reduce max line length to 100

Steps to reproduce:

1. setting `vim.highlight.on_yank`
   ```
   vim.api.nvim_create_autocmd({ "TextYankPost" }, {
     pattern = { "*" },
     callback = function()
       vim.highlight.on_yank({ timeout = 200 })
     end,
   })
   ```
2. repeat typing `yeye` ...
3. causes the following error.
   ```
   Error executing vim.schedule lua callback: vim/_editor.lua:0: handle 0x01e96970 is already closing
   stack traceback:
           [C]: in function 'close'
           vim/_editor.lua: in function ''
           vim/_editor.lua: in function <vim/_editor.lua:0>
   ```

📝 Test result before fix:

    [----------] Global test environment setup.
    [----------] Running tests from test/functional/lua/highlight_spec.lua
    [ RUN      ] vim.highlight.on_yank does not show errors even if buffer is wiped before timeout: 15.07 ms OK
    [ RUN      ] vim.highlight.on_yank does not show errors even if executed between timeout and clearing highlight: 15.07 ms ERR
    test/helpers.lua:73: Expected objects to be the same.
    Passed in:
    (string) 'Error executing vim.schedule lua callback: vim/_editor.lua:0: handle 0x02025260 is already closing
    stack traceback:
            [C]: in function 'close'
            vim/_editor.lua: in function ''
            vim/_editor.lua: in function <vim/_editor.lua:0>'
    Expected:
    (string) ''

vim.fs.parents() is a Lua iterator that returns the next parent
directory of the given file or directory on each iteration.

- Complete function:
  There was lots of unnecessary C code for the complete function, therefore
  moving it to Lua and use all the plumbing we have in place to retrieve the
  results.
- Moving the module:
  It's important we keep nvim lua modules name spaced, avoids conflict with
  plugins, luarocks, etc.

perf(_editor): no need to stop inside vim.defer_fn