[anthropic] fix issue #1370 with tool call duplication

[mmazurkevich]

Without this fix during the stream event handling when EventType.MESSAGE_STOP occurs, the latest content block was resent again and it caused to the additional tool call(if it was the latest event)
Also I've described the root cause in the comment to the issue

[ilayaperumalg]

@mmazurkevich Thanks for debugging and submitting the PR to fix the issue.

[mmazurkevich]

@ilayaperumalg I've updated the formatting and force-pushed the changes because of the failed GH Action

[ilayaperumalg]

@mmazurkevich With this change, some of the stream+toolcalling tests are failing:

AnthropicChatClientIT#streamFunctionCallTest
AnthropicChatModelIT#streamFunctionCallTest
AnthropicChatModelIT#streamFunctionCallUsageTest

Could you check?

[mmazurkevich]

@ilayaperumalg thank you for the ping. The failed test highlighted the problem that was in the code even before the change. Previously, internalStream used switchMap to process ChatCompletionResponses, which caused the active stream (including potential recursive calls) to be canceled whenever a new response arrived. This led to incomplete processing of streaming tool calls and unexpected behavior when handling tool_use events.

The fix has been pushed. Also, I've run all 50 tests locally with my own ANTHROPIC_API_KEY looks like all of them passed

[ilayaperumalg]

@mmazurkevich Thank you so much for the quick response, fixing the issue and verifying all the tests! I will get this merged soon.