perf(specialize): widen BINARY_OP_ADD_INT specialization to int64 range

Change the add specialization condition from _PyLong_CheckExactAndCompact to _PyLong_CheckExactAndFitsInt64 so that exact int operands in the full int64 range (not just compact/single-digit values) are specialized to BINARY_OP_ADD_INT.

Subtract and multiply retain their compact-only conditions.

Author: KRRT7

Python/specialize.c

@@ -2350,7 +2350,7 @@ _Py_Specialize_BinaryOp(_PyStackRef lhs_st, _PyStackRef rhs_st, _Py_CODEUNIT *in
                 specialize(instr, BINARY_OP_ADD_UNICODE);
                 return;
             }
-            if (_PyLong_CheckExactAndCompact(lhs) && _PyLong_CheckExactAndCompact(rhs)) {
+            if (_PyLong_CheckExactAndFitsInt64(lhs) && _PyLong_CheckExactAndFitsInt64(rhs)) {
                 specialize(instr, BINARY_OP_ADD_INT);
                 return;
             }