Add general purpose `ARRAY_SIZE` macro

This commit adds `ARRAY_SIZE` as an helper for determining the number of
elements in an initialized array. The calculation is the same but the
macro provides a convenient shortcut. The implementation was borrowed
from the kernel sources.

src/suricata-common.h

@@ -494,5 +494,8 @@ char *strptime(const char * __restrict, const char * __restrict, struct tm * __r
 extern int coverage_unittests;
 extern int g_ut_modules;
 extern int g_ut_covered;
+
+#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
+
 #endif /* __SURICATA_COMMON_H__ */