Fix creation of Bucket Transforms with pydantic>=2.11.0

When using pydantic>=2.11.0, we get an error when creating bucket
transforms. In this version, it's illegal to access self before calling
super. To fix this, we just need to ensure we call `super().__init__`
before setting field properties on `self`.

Author: Zac Sanchez

pyiceberg/transforms.py

@@ -234,8 +234,8 @@ class BucketTransform(Transform[S, int]):
     _num_buckets: PositiveInt = PrivateAttr()
 
     def __init__(self, num_buckets: int, **data: Any) -> None:
-        self._num_buckets = num_buckets
         super().__init__(f"bucket[{num_buckets}]", **data)
+        self._num_buckets = num_buckets
 
     @property
     def num_buckets(self) -> int: