Python: Avro write support

[Fokko]

Feature Request / Improvement

In order to write a ManifestList (List[ManifestFile]) and ManifestFile (List[ManifestEntry]) we need to have the ability to write Avro.

• Construct the pyiceberg/avro/encoder.py that encodes the Python primitives into bytes, according to the Avro spec: https://avro.apache.org/docs/1.11.1/specification/. Also the Python Avro implementation is a good source for inspiration: https://github.com/apache/avro/blob/master/lang/py/avro/io.py#L415
• Similar to the read path, we need to construct a writer, see resolver.py:construct_reader for reference, and this will return a Writer.
• The writer will accept an Encoder and by passing in List[ManifestFile] and List[ManifestEntry] we'll be able to write the datums to Avro.

Query engine

None

[ggbaro]

@dariocurr @emanueledomingo @enryls

[Fokko]

Fixed in #7873