Review reporter TraceEventMeta structure fields

**After Profiles alpha**

1. ProcessName seems to be a dead field, only found reference in base_reporter_test.go

2. Some fields within the TracerEventMeta can be removed by embedding ResourceKey and SampleKey structs (deduplicated).

_Originally posted by @rogercoll in https://github.com/open-telemetry/opentelemetry-ebpf-profiler/pull/1234#discussion_r2965258468_
            