feat: Update WatsonXChatGenerator to use the StreamingChunk fields

[maxdswain]

Related Issues

• fixes feat: Update WatsonXChatGenerator to use the StreamingChunk fields #2217 & feat: Update our ChatGenerators in integrations to use the new StreamingChunk fields #2070

Proposed Changes:

feat: Update WatsonXChatGenerator to use the StreamingChunk index and finish_reason fields.

How did you test it?

Updated existing tests.

Notes for the reviewer

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test:.

[anakin87]

Thanks for the contribution!

I think that a little more adaptation work will be needed, especially in handling tool calls.

I suggest taking inspiration from #2078 and #2108 (but keeping in mind that each provider has its own particularities and code can be very different).

Also, I'd like to see a test with real chunks coming from WatsonX (similar test for Google GenAI).

[maxdswain]

Thanks for the contribution!

I think that a little more adaptation work will be needed, especially in handling tool calls.

I suggest taking inspiration from #2078 and #2108 (but keeping in mind that each provider has its own particularities and code can be very different).

Also, I'd like to see a test with real chunks coming from WatsonX (similar test for Google GenAI).

Okay, I'll convert it to a draft for now and work on it a bit more to add support for tool calls as well as more tests. I'll let you know when it's ready.