refactor: format all C files under nvim/ #15977

* refactor: format all C files under nvim
* refactor: disable formatting for Vim-owned files:
    * src/nvim/indent_c.c
    * src/nvim/regexp.c
    * src/nvim/regexp_nfa.c
    * src/nvim/testdir/samples/memfile_test.c

src/nvim/terminal.h

@@ -1,8 +1,8 @@
 #ifndef NVIM_TERMINAL_H
 #define NVIM_TERMINAL_H
 
-#include <stddef.h>
 #include <stdbool.h>
+#include <stddef.h>
 #include <stdint.h>
 
 typedef struct terminal Terminal;