Fix overflow of rdbWriteRaw return value (#8306)

Saving string of more than 2GB to the RDB file, can result in corrupt RDB, or failure in rdbSave.
S

(cherry picked from commit 542455ce2a)

src/rdb.c

@@ -84,7 +84,7 @@ void rdbReportError(int corruption_error, int linenum, char *reason, ...) {
     exit(1);
 }
 
-static int rdbWriteRaw(rio *rdb, void *p, size_t len) {
+static ssize_t rdbWriteRaw(rio *rdb, void *p, size_t len) {
     if (rdb && rioWrite(rdb,p,len) == 0)
         return -1;
     return len;