refactor: remove highlight + palette autoload

Move autoloaded palette, highlight to color/srcery.vim.

We don't have to reference this in multiple script files, so I've moved
it back into the main colors file

autoload/srcery/helper.vim

@@ -22,50 +22,4 @@ function! srcery#helper#GetColor(group, ...) abort
   return [ l:gui_color, l:term_color ]
 endfunction
 
-function! srcery#helper#Highlight(group, fg, ...) abort
-  " Arguments: group, guifg, guibg, gui, guisp
-
-  " foreground
-  let l:fg = a:fg
-
-  " background
-  if a:0 >= 1
-    let l:bg = a:1
-  else
-    let l:bg = g:srcery#palette.none
-  endif
-
-  " emphasis
-  if a:0 >= 2 && strlen(a:2)
-    let l:emstr = a:2
-  else
-    let l:emstr = 'NONE,'
-  endif
-
-  " special fallback
-  if a:0 >= 3
-    if g:srcery_guisp_fallback !=# 'NONE'
-      let fg = a:3
-    endif
-
-    " bg fallback mode should invert higlighting
-    if g:srcery_guisp_fallback ==# 'bg'
-      let emstr .= 'inverse,'
-    endif
-  endif
-
-  let l:histring = [ 'hi', a:group,
-        \ 'guifg=' . l:fg[0], 'ctermfg=' . l:fg[1],
-        \ 'guibg=' . l:bg[0], 'ctermbg=' . l:bg[1],
-        \ 'gui=' . l:emstr[:-2], 'cterm=' . l:emstr[:-2]
-        \ ]
-
-  " special
-  if a:0 >= 3
-    call add(l:histring, 'guisp=' . a:3[0])
-  endif
-
-  execute join(l:histring, ' ')
-endfunction
-
 " vim: fdm=marker ts=2 sts=2 sw=2 fdl=0: