feat: add ingestion_metadata field

[liuyang1520]

Summary

• feat: add ingestion_metadata field

Add this option in the configuration, which can be used in the library wrapper/code generation/dynamic loading cases, for setting the ingestion_metadata information.

No need to add to example as this field in internal measurement usage only.

Tests

Local tests with echo server:

--> {"api_key":"test","events":[{"event_type":"Button Clicked","user_id":"user-id","time":1663295517696,"insert_id":"38667e69-ff39-42ab-9942-7a37d05ca176","library":"amplitude-go/0.0.7","ingestion_metadata":{"source_name":"test source name","source_version":"2.0.0"}},{"event_type":"type-of-event","user_id":"user-id","device_id":"device-id","time":1663295517704,"insert_id":"f25db244-9a00-49c5-b297-45e3d9a5e7c7","library":"amplitude-go/0.0.7","ingestion_metadata":{"source_name":"test source name","source_version":"2.0.0"},"event_properties":{"source":"notification"}}]}

Checklist

• [x] Does your PR title have the correct title format?
• Does your PR have a breaking change?: No