Support DIGEST-MD5 / delegation token authentication for HMS

[ShreyeshArangath]

Feature Request / Improvement

Summary

PyIceberg's HiveCatalog supports Kerberos (GSSAPI) authentication via hive.kerberos-authentication, but does not support DIGEST-MD5 SASL authentication with Hadoop delegation tokens. In many production Hadoop environments, pods/containers authenticate to HMS using delegation tokens (read from $HADOOP_TOKEN_FILE_LOCATION) rather than Kerberos keytabs. This means PyIceberg's Hive catalog cannot be used in these environments without building a custom client.

Proposed Enhancement

Extend _HiveClient to support DIGEST-MD5 delegation token auth:

1. Add a new config property (e.g. hive.metastore.authentication=DIGEST-MD5)
2. When DIGEST-MD5 is configured, read credentials from $HADOOP_TOKEN_FILE_LOCATION (Hadoop Writable credentials format)
3. Use TSaslClientTransport with mechanism=DIGEST-MD5 and the extracted token identifier/password