RPC: adopt system-specific naming practices

[lmolkova]

Implement #1708 for RPC

See https://github.com/open-telemetry/semantic-conventions/blob/main/docs/general/naming.md#system-specific-naming and #1734 for the details

• rename rpc.system to rpc.protocol|system|framework|etc.name
• review RPC system list and clean it up
• remove rpc prefix from system-specific conventions

[steverao]

Following the discussion of RPC stability on September 25, 2025 (CST), I would like to add some comments regarding point one, based on my investigation of the Apache Dubbo framework’s protocols.

1. In Dubbo 3.x, a native protocol called Triple has been implemented based on gRPC, allowing Dubbo clients to directly invoke gRPC servers and vice versa. For more details, please refer to the related documentation. Additionally, this demo illustrates how to use the Triple protocol, and the trace structure appears as follows:
2. Besides Triple, Dubbo also provides another native protocol named Dubbo, which is based on TCP and was introduced in version 2.x.

Based on above information, I suggest renaming rpc.system to rpc.protocol.name. It can tell the users the specific communication protocol of Dubbo application. We can use otel.scope.name to record framework-specific information just like mentioned by @trask