Replace gen_ai.system with gen_ai.provider.name in AWS SDK instrumentation

[yuliia-fryshko]

While working on the Bedrock instrumentation, we were using gen_ai.system as a span attribute. However, according to the OpenTelemetry semantic conventions for GenAI agent spans
, gen_ai.system has been replaced by gen_ai.provider.name.

Describe the solution you'd like to see

I’d like to replace gen_ai.system with gen_ai.provider.name in the AWS SDK instrumentation.
Additionally, we have to review and ensure that all fields in the Bedrock instrumentation align with the latest semantic conventions.