Add length check before content comparison in equalStringObjects (#14062)

### Issue 

Previously, even when only string equality needed to be determined, the
comparison logic still performed unnecessary `memcmp()` calls to check
string ordering, even if the lengths were not equal.

### Change
This PR add length check before content comparison in
`equalStringObjects` function.

---------

Co-authored-by: debing.sun <debing.sun@redis.com>

src/object.c

@@ -980,7 +980,7 @@ int collateStringObjects(const robj *a, const robj *b) {
 
 /* Equal string objects return 1 if the two objects are the same from the
  * point of view of a string comparison, otherwise 0 is returned. Note that
- * this function is faster then checking for (compareStringObject(a,b) == 0)
+ * this function is faster than checking for (compareStringObject(a,b) == 0)
  * because it can perform some more optimization. */
 int equalStringObjects(robj *a, robj *b) {
     if (a->encoding == OBJ_ENCODING_INT &&
@@ -989,6 +989,11 @@ int equalStringObjects(robj *a, robj *b) {
          * long is the same. */
         return a->ptr == b->ptr;
     } else {
+        if (sdsEncodedObject(a) && sdsEncodedObject(b)
+            && sdslen(a->ptr) != sdslen(b->ptr))
+        {
+            return 0;
+        }
         return compareStringObjects(a,b) == 0;
     }
 }