Fix polyglot ftdetect as fallback for native vim

Fix ftdetect for ft ext defined only by native vim, e.g.
`*.jjdescription`, `*.http`, `*.mysql_history`, & others

It seems vim-polyglot loads vim-`filetype.vim` then clobbers it by
"resetting" with `au! filetypedetect` afterwards, even though
vim-polyglot intends to be a fallback, according to comments in
`init.vim`

This is evidenced by `*.jjdescription`, `*.http`, and `.mysql_history`,
filetype extensions defined in vim-`filetype.vim` but not
polyglot-`filetype.vim`:

    vim -c "redir >> /dev/stdout" -c "set filetype?" -c "redir END" -c "sleep 3" -c "quit" foo.jjdescription
    vim -c "redir >> /dev/stdout" -c "set filetype?" -c "redir END" -c "sleep 3" -c "quit" foo.http
    vim -c "redir >> /dev/stdout" -c "set filetype?" -c "redir END" -c "sleep 3" -c "quit" .mysql_history

Compare:

    vim --clean -c "redir >> /dev/stdout" -c "set filetype?" -c "redir END" -c "sleep 3" -c "quit" foo.jjdescription
    vim --clean -c "redir >> /dev/stdout" -c "set filetype?" -c "redir END" -c "sleep 3" -c "quit" foo.http
    vim --clean -c "redir >> /dev/stdout" -c "set filetype?" -c "redir END" -c "sleep 3" -c "quit" .mysql_history

And:

    vim -c "redir >> /dev/stdout" -c "set filetype?" -c "redir END" -c "sleep 3" -c "quit" foo.py
    vim -c "redir >> /dev/stdout" -c "set filetype?" -c "redir END" -c "sleep 3" -c "quit" foo.bash
    vim -c "redir >> /dev/stdout" -c "set filetype?" -c "redir END" -c "sleep 3" -c "quit" foo.js

Note although vim-polyglot does not define `bash.vim` nor
`javascript.vim`, polyglot-`filetype.vim` does define the `*.bash` and
`*.js` extensions, so they "still work"

I'm using `vim --version` and vim-plug:

    VIM - Vi IMproved 9.1 (2024 Jan 02, compiled May 23 2025 00:48:59)
    Included patches: 1-948, 950-1230, 1242, 1244

Tried to retain original intent to first load poly-`filetype.vim` then
vim-`filetype.vim` on top. Early workarounds:
 * disable vim-polyglot ftdetect `let g:polyglot_disabled = ['ftdetect']`
 * `init.vim`: comment out `au! filetypedetect`
 * `init.vim`: comment out `Load user-defined...` and `Prevent filetype.vim...` paragraphs

Unsure how to test "vim-`filetype.vim` loads first case", which seems
related to [handling nvim and other package managers](sheerun/issues/706#issuecomment-826067169),
which I haven't done

My print debugging output below, indentations for clarity.

Before:
```
poly filetype.vim start
  init.vim start
    init.vim did_load_polyglot: false
    init.vim runtime! filetype.vim
      poly filetype.vim start
	init.vim init() no-op
      poly filetype.vim end
      vim filetype.vim start
	init.vim init() no-op
      vim filetype.vim end
    init.vim init() no-op
    init.vim did_load_filetypes: true
  init.vim end
  init.vim init() no-op
poly filetype.vim end
vim filetype.vim start
vim filetype.vim finish early
polyglot.vim start
  init.vim init() no-op
polyglot.vim finish
```

After:
```
poly filetype.vim start
  init.vim start
    init.vim did_load_polyglot: false
    init.vim did_load_filetypes: false
  init.vim end
  init.vim init() no-op
poly filetype.vim end
vim filetype.vim start
  init.vim init() no-op
vim filetype.vim end
polyglot.vim start
  init.vim init() no-op
polyglot.vim finish
```

Related: sheerun#706, sheerun#758, sheerun#756, sheerun#871, NoahTheDuke/vim-just#125
Fix: sheerun#877, sheerun#829, sheerun#845, sheerun#817

Author: Kache

autoload/polyglot/init.vim

@@ -142,14 +142,6 @@ if exists('s:cpo_save')
   unlet s:cpo_save
 endif
 
-" Load user-defined filetype.vim and oter plugins ftdetect first
-" This is to use polyglot-defined ftdetect always as fallback to user settings
-augroup filetypedetect
-  runtime! filetype.vim
-  runtime! ftdetect/*.vim
-augroup END
-
-
 augroup filetypedetect
 
 " Switch to compatible mode for the time being
@@ -161,11 +153,17 @@ if !has_key(g:polyglot_is_disabled, 'ftdetect')
 " It can happen vim filetype.vim loads first, then we need a reset
 if exists("did_load_filetypes")
   au! filetypedetect
-endif
 
-" Prevent filetype.vim of vim from loading again
-let did_load_filetypes = 1
+  " Load user-defined filetype.vim and other plugins ftdetect first
+  " This is to use polyglot-defined ftdetect always as fallback to user settings
+  augroup filetypedetect
+    runtime! filetype.vim
+    runtime! ftdetect/*.vim
+  augroup END
 
+  " Prevent filetype.vim of vim from loading again
+  let did_load_filetypes = 1
+endif
 
 " DO NOT EDIT CODE BELOW, IT IS GENERATED WITH MAKEFILE