Add gRPC Swift 2 capture support

[NghiaTranUIT]

Summary

• Add support for capturing gRPC traffic from Swift 2 clients
• Update the network injector and transport handling to recognize and package gRPC events
• Refresh the public API, message model, and package metadata for the new flow
• Update README guidance and add coverage in the test suite

Testing

• Added/updated unit tests for gRPC event capture and message handling
• Not run (not requested)