fix(telemetry)!: update RPC semantic convention keys

[rkargMsft]

Updates Orleans RPC activity attributes to the current OpenTelemetry semantic conventions. Replaces legacy and reserved-namespace keys, preserves Orleans service/target/source metadata under the Orleans namespace, versions the affected ActivitySources, and adds regression coverage.

Semantic Convention for non-standard attributes is to prefix with something company or product specific. Using orleans.** which is also a pattern in use for other existing attributes.

Fixes #10320

[ReubenBond]

Pushed bb756333e to fully qualify the rpc.method attribute as <interface>/<method>. The current OpenTelemetry RPC semantic conventions deprecate the separate rpc.service attribute and require the logical service name to be included in rpc.method; emitting only the method name would leave the updated telemetry non-conformant. The regression test now verifies the fully qualified value.

[rkargMsft]

Pushed bb756333e to fully qualify the rpc.method attribute as <interface>/<method>. The current OpenTelemetry RPC semantic conventions deprecate the separate rpc.service attribute and require the logical service name to be included in rpc.method; emitting only the method name would leave the updated telemetry non-conformant. The regression test now verifies the fully qualified value.

In that case then do we need the orleans.rpc.service attribute?