GH-35112: [Python] Expose keys_sorted in python MapType (#35113)

### Rationale for this change

It not possible to read `keys_sorted` in the python API

### What changes are included in this PR?

- expose keys_sorted in `cdef class MapType` / types.pxi
- add tests

### Are these changes tested?

yes

### Are there any user-facing changes?

We're exposing keys_sorted but I guess the documentation will update itself from the `"""` pydoc (?)

This is not an API breaking change

* Closes: #35112

Authored-by: aandres <aandres@tradewelltech.co>
Signed-off-by: Alenka Frim <frim.alenka@gmail.com>

python/pyarrow/tests/test_types.py

@@ -580,6 +580,10 @@ def test_map_type():
     assert ty == ty_metadata
     assert not ty.equals(ty_metadata, check_metadata=True)
 
+    for keys_sorted in [True, False]:
+        assert pa.map_(pa.utf8(), pa.int32(),
+                       keys_sorted=keys_sorted).keys_sorted == keys_sorted
+
     with pytest.raises(TypeError):
         pa.map_(None)
     with pytest.raises(TypeError):

python/pyarrow/types.pxi

@@ -536,6 +536,19 @@ cdef class MapType(DataType):
         """
         return pyarrow_wrap_data_type(self.map_type.item_type())
 
+    @property
+    def keys_sorted(self):
+        """
+        Should the entries be sorted according to keys.
+
+        Examples
+        --------
+        >>> import pyarrow as pa
+        >>> pa.map_(pa.string(), pa.int32(), keys_sorted=True).keys_sorted
+        True
+        """
+        return self.map_type.keys_sorted()
+
 
 cdef class FixedSizeListType(DataType):
     """