sqlite3: Add sequence methods to Blob (#7684)

python/cppython#91599

Author: JelleZijlstra

stdlib/sqlite3/dbapi2.pyi

@@ -460,3 +460,5 @@ if sys.version_info >= (3, 11):
         def __len__(self) -> int: ...
         def __enter__(self: Self) -> Self: ...
         def __exit__(self, __typ: object, __val: object, __tb: object) -> Literal[False]: ...
+        def __getitem__(self, __item: SupportsIndex | slice) -> bytes: ...
+        def __setitem__(self, __item: SupportsIndex | slice, __value: ReadableBuffer) -> None: ...