Lua API: Unify server env checks and fix missing ones (#16457)

A few functions tried to dereference a ServerEnvironment nullptr by
calling 'getEnv()'. This change makes use of a macro where possible.

This also cleans up incorrect macro uses, with no functional difference.

src/script/lua_api/l_internal.h

@@ -44,8 +44,11 @@
 #define GET_ENV_PTR_NO_MAP_LOCK                              \
 	DEBUG_ASSERT_NO_CLIENTAPI;                               \
 	ServerEnvironment *env = (ServerEnvironment *)getEnv(L); \
-	if (env == NULL)                                         \
-		return 0
+	if (!env) {                                              \
+		log_deprecated(L, "Calling this function during script init is disallowed.", 1); \
+		return 0;                                            \
+	} \
+	((void)0)
 
 // Retrieve ServerEnvironment pointer as `env`
 #define GET_ENV_PTR         \