Update OTEL dotnet mappings to include process information

[IGx89]

OpenTelemetry.Instrumentation.Process adds some new process metrics following Semantic Convention v1.25.0:

• process.cpu.time
• process.memory.virtual
• process.thread.count

There currently are no mappings for those metrics to their corresponding Datadog metrics:

• runtime.dotnet.cpu.system
• runtime.dotnet.cpu.user
• runtime.dotnet.cpu.percent
• runtime.dotnet.mem.committed
• runtime.dotnet.threads.count

Is it possible to add that?

[IGx89]

Various OTEL process metrics are being renamed in .NET 9 it looks: open-telemetry/opentelemetry-dotnet-contrib#2339. See https://learn.microsoft.com/en-us/dotnet/core/diagnostics/built-in-metrics-runtime for the official docs on them. Given that, I'd recommend mapping these metric names instead:

• dotnet.process.cpu.time
• dotnet.process.memory.working_set
• dotnet.thread_pool.thread.count

Other already-mapped metrics are renamed in .NET 9 too, requiring further updates to the mappings too.