feat: complete namespace support for Glue (#158)

This PR adds the remaining namespace operations to the glue namespace
implementation. We previously only had listing support, now we've got
the full namespace level support.

Operations:
  - createNamespace - supports CREATE/EXIST_OK/OVERWRITE modes
- dropNamespace - supports FAIL/SKIP modes with RESTRICT/CASCADE
behaviors
  - describeNamespace - get namespace properties and metadata
  - namespaceExists - check if a namespace exists

Author: geruh