vim ftplugins like vimtex not working with "native" plugin manager

[timokau]

Issue description

There is some weirdness going on that causes the plugins loaded by the native pluginmanager to be loaded after the default filetype plugins. Other package managers will load it before that. Because of that, vimtex won't work (lervag/vimtex#586).

I've created an upstream issue for this: neovim/neovim#9390

Steps to reproduce

Try to install vimtex with the native plugin manager, open a .tex file and observe that none of the vimtex commands are loaded and :scriptnames shows vimtex being loaded after the default tex.vim.

Technical details

Please run nix-shell -p nix-info --run "nix-info -m" and paste the
results.

[timokau]

Duplicate of #39364.