Add automatic request header support

[tconley1428]

Summary

• Cherry-picked automatic request header support from temporal-api-go repository (commit d43d11d83b42eb29d2bee12dcad934eabc0166e8)
• Adds ExtractTemporalRequestHeaders functionality to automatically extract headers from request messages
• Generates headers based on proto annotations for temporal-namespace and temporal-resource-id

Key Changes

• cmd/proxygenerator/request_header.go: Header generation code that parses proto annotations
• cmd/proxygenerator/main.go: Updated to include request header generation in build process
• proxy/request_header.go: Generated code that extracts headers from various workflow/activity requests
• proxy/request_header_test.go: Comprehensive test coverage for header extraction functionality

Test plan

• Verify all existing tests continue to pass
• Run the proxy generator to ensure no compilation errors
• Test header extraction for various request types (StartWorkflowExecution, GetWorkflowExecutionHistory, etc.)
• Validate namespace and resource-id headers are properly extracted
• Confirm existing metadata is respected and not overwritten

🤖 Generated with Claude Code