vim-patch:8.2.3944: insert mode completion functions are too long

Problem:    Insert mode completion functions are too long.
Solution:   Split up into multiple functions. (Yegappan Lakshmanan,
            closes vim/vim#9431)
5d2e007ccb

Cherry-pick can_cindent_get() -> get_can_cindent() from patch 8.1.2062.

src/nvim/edit.c

@@ -5654,7 +5654,7 @@ static char_u *do_insert_char_pre(int c)
   return res;
 }
 
-bool can_cindent_get(void)
+bool get_can_cindent(void)
 {
   return can_cindent;
 }