A centralized list for these renames is not good because:
- It breaks disabledModules for modules that have a rename defined
- Adding/removing renames for a module means having to find them in the
central file
- Merge conflicts due to multiple people editing the central file
From https://github.com/zsh-users/zsh-syntax-highlighting#faq:
"It must be sourced after all custom widgets have been created
(i.e., after all zle -N calls and after running compinit)."
zsh-syntax-highlighting must be sourced to the end.
Right now the `programs.zsh.syntax-highlighting.highlighters` option
lacks appropriate validation which can cause confusing things when
mistyping a higlighter for zsh-syntax-highlighting.
* programs.zsh: factor zsh-syntax-highlighting out into its own module
* programs.zsh.syntax-highlighting: add `highlighters` option
* programs.zsh: document BC break introduced by moving zsh-syntax-completion into its own module
