[java][python] IBM watsonx.ai chat model integration

[cansuk99]

Linked issue: #902

Purpose of change

Chat model integration for watsonx.ai models provided by IBM Cloud.

• Adds a new watsonx integration module for Java chat models.
• Adds a new watsonx integration module for Python chat models.
• Adds watsonx resource names and YAML alias mappings in both Java and Python.
• Updates distribution and build wiring to include the new integration artifact.
• Adds documentation for watsonx setup, parameters, model usage, and YAML alias support.

Tests

Java:

• Watsonx connection behavior and payload conversion tests.
• Watsonx setup validation tests.
• Alias resolution tests for watsonx.

Python:

• Watsonx chat behavior tests (mocked tool-call, retry flows).
• Alias resolution tests for watsonx.

Both Java and Python integrations were tested live with IBM Cloud credentials with flink jobs running on k8s.

Documentation

• doc-needed
• doc-not-needed
• doc-included