Add genai upload hook to genai utils following semconv v1.37

[aabmass]

Child of #3065, this issue tracks implementation since there is a lot of discussion there already.

Implement SemConv v1.37 uploading content to external storage.

• Define the type that hooks should implement Define genai content uploader hook and entry point #3752
• Add an entry point + environment variable to select the hook, with a util for instrumentations to load the hook Define genai content uploader hook and entry point #3752
• Implement a simple vendor agnostic hook with fsspec. Fsspec can handle uris like /local/path, s3://bucket, gs://bucket etc. It will implement refs in Add gen_ai _ref attributes for referencing external uploaded content semantic-conventions#2750 Add fsspec gen ai upload hook #3759
• Add references to the uploaded data on the logs and spans Stamp uploaded references refs onto spans and logs #3763

This is based on the PoC here main...aabmass:opentelemetry-python-contrib:adk-sample. I mostly need to work out queueing which should probably go through a path on the local filesystem.