Move all filetype specific includes to ftplugin

[ClashTheBunny]

What

Move all filetype specific includes to ftplugin

Why

• possibly more performant per https://stackoverflow.com/questions/7863804/autocmd-filetype-vs-ftplugin

• cleaner - cluttering the root directory with files is adds to cognitive load.

Impact

None to the best of my knowledge.

[lollipopman]

looks good, the only downside I have experienced is that it is more difficult to override settings with ~/.vimrc_local, when you use ftplugins, I think last time I needed to do that I used ~/.vim/after/ftplugin/<filetype>.vim