[EventPipe][User_events] Add MetadataID and ProviderName to metadata bytes #118294
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Pull Request Overview
This PR modifies the EventPipe metadata serialization to include the ProviderName as part of the metadata payload, aligning with the NetTrace format specification. The key change addresses a gap where the ProviderName wasn't being prepended to metadata blocks as required for proper event-to-metadata correlation.
- Adds ProviderName (UTF-16 string) to the metadata payload structure
- Updates metadata length calculation to include the provider name size
- Adjusts the maximum iovec array size to accommodate the additional metadata component
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noahfalk
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Updating docs in response to dotnet/runtime#117686 and dotnet/runtime#118294
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In constructing metadata in #115265, it was missed that ProviderName and Metadata ID are prepended to the metadata block instead of being a part of the EventPipeEvent's Metadata. Those two fields assist in correlating Event blocks with Metadata blocks as specified in https://github.com/microsoft/perfview/blob/main/src/TraceEvent/EventPipe/NetTraceFormat_v5.md#metadata-event-encoding.
For User_events EventPipe scenarios, the metadata will be inlined with the event, so there is no need for a MetadataID, and thus we will only prepend the ProviderName to avoid having to encode an unused uint32_t.
Testing