Feat: anthropic thinking json to stream transform

[VisargD]

Title: Feat: anthropic thinking json to stream transform

🔄 What Changed

• Fixed bug in Anthropic and Vertex AI providers to correctly check for partial_json using undefined check instead of truthy check
• Added caching support for Anthropic thinking responses
• Enhanced Bedrock chat completion to check for empty content blocks
• Added comprehensive support for content_blocks in OpenAI chat completion JSON to stream transformation
• Created new ContentBlockChunk type definition

🔍 Impact of the Change

• Improves handling of streaming responses from various AI providers
• Enables proper transformation of JSON responses with thinking blocks to stream format
• Ensures empty tool call chunks are handled correctly
• Provides better support for content blocks in streaming responses

📁 Total Files Changed

• 5 files modified with 122 additions and 4 deletions

🧪 Test Added

N/A

🔒 Security Vulnerabilities

N/A

Motivation:

• Fixes issues with Anthropic thinking feature and JSON streaming transformations
• Improves compatibility with various AI provider response formats
• Enhances support for content blocks in streaming responses

Related Issues:
N/A

[VisargD]

Created this PR from the existing PR with some minor changes: #1005 @narengogi