vim: Load other always-on plugins too

And move the plugin specific keybindings into 40-keybindings.vim.
`packloadall` sources the plugins directly in contrast to `packadd`.
Because of that we can access the `g:loaded_*` variables and do not have
to specify our own keybindings for vim-surround as now the user bindings
are loaded later and overwrite possible clashes.

.config/vim/pack/plugins/start/fzf

@@ -0,0 +1 @@
+../opt/fzf

.config/vim/pack/plugins/start/fzf.vim

@@ -0,0 +1 @@
+../opt/fzf.vim

.config/vim/pack/plugins/start/vim-gutentags

@@ -0,0 +1 @@
+../opt/vim-gutentags/

.config/vim/pack/plugins/start/vim-surround

@@ -0,0 +1 @@
+../opt/vim-surround/