[3.14] gh-139283: correctly handle size limit in cursor.fetchmany() (GH-139296) (GH-139441)

Passing a negative or zero size to `cursor.fetchmany()` made it fetch all rows
instead of none.

While this could be considered a security vulnerability, it was decided to treat
this issue as a regular bug as passing a non-sanitized *size* value in the first
place is not recommended.
(cherry picked from commit bc172ee830)

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
Co-authored-by: Petr Viktorin <encukou@gmail.com>

Modules/_sqlite/cursor.h

@@ -35,7 +35,7 @@ typedef struct
     pysqlite_Connection* connection;
     PyObject* description;
     PyObject* row_cast_map;
-    int arraysize;
+    uint32_t arraysize;
     PyObject* lastrowid;
     long rowcount;
     PyObject* row_factory;