refactor: eliminate misc2.c

move `call_shell` to misc1.c
Move some fns to state.c
Move some fns to option.c
Move some fns to memline.c
Move `vim_chdir*` fns to file_search.c
Move some fns to new module, bytes.c
Move some fns to fileio.c

src/nvim/strings.c

@@ -5,7 +5,6 @@
 #include "nvim/vim.h"
 #include "nvim/ascii.h"
 #include "nvim/strings.h"
-#include "nvim/misc2.h"
 #include "nvim/file_search.h"
 #include "nvim/buffer.h"
 #include "nvim/charset.h"