Removing then adding the same partition in update_spec fails #1131

Apache Iceberg version

0.7.1 (latest release)

Please describe the bug 🐞

When adding a field to partition spec, if the field previously existed but was deleted it will fail when not explictly defining a column name:

For example this would fail:
table.update_spec().add_identity("VendorID").commit()
table.update_spec().remove_field("VendorID").commit()
table.update_spec().add_identity("VendorID").commit()

This would fail:
table.update_spec().add_field("VendorID", IdentityTransform()).commit()
table.update_spec().remove_field("VendorID").commit()
table.update_spec().add_field("VendorID", IdentityTransform()).commit()

This would not fail when defining the partition field name:
table.update_spec().add_field("VendorID", IdentityTransform(), "VendorID").commit()
table.update_spec().remove_field("VendorID").commit()
table.update_spec().add_field("VendorID", IdentityTransform(), "VendorID").commit()

Example trace:
Traceback (most recent call last):
File "C:\Users\a\PycharmProjects\pythonProject\test.py", line 24, in
table.update_spec().add_identity("VendorID").commit()
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\a\PycharmProjects\pythonProject.venv\Lib\site-packages\pyiceberg\table_init_.py", line 3682, in add_identity
return self.add_field(source_column_name, IdentityTransform(), None)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\a\PycharmProjects\pythonProject.venv\Lib\site-packages\pyiceberg\table_init_.py", line 3657, in add_field
new_field = self.partition_field((bound_ref.field.field_id, transform), partition_field_name)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\a\PycharmProjects\pythonProject.venv\Lib\site-packages\pyiceberg\table_init.py", line 3833, in _partition_field
return PartitionField(source_id, field_key[1], transform, name)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\a\PycharmProjects\pythonProject.venv\Lib\site-packages\pyiceberg\partitioning.py", line 111, in init
super().init(**data)
File "C:\Users\a\PycharmProjects\pythonProject.venv\Lib\site-packages\pydantic\main.py", line 193, in init
self.pydantic_validator.validate_python(data, self_instance=self)
pydantic_core._pydantic_core.ValidationError: 1 validation error for PartitionField
name
Field required [type=missing, input_value={'source-id': 1, 'field-i...m': IdentityTransform()}, input_type=dict]
For further information visit https://errors.pydantic.dev/2.8/v/missing