[DiagnosticsClient] Update APIs

[mdh1418]

While adding documentation for the SupportsEventPipeUserEventsCommand APIs (https://github.com/dotnet/diagnostics/pull/5656), I figured I should update all public APIs from Microsoft.Diagnostics.NETCore.Client's DiagnosticsClient class.

The intent is to merge this PR after the next Microsoft.Diagnostics.NETCore.Client release containing the SupportsEventPipeUserEventsCommand APIs.

Update: The plan is to keep SupportsEventPipeUserEventsCommand as an internal API utilized by dotnet-trace collect-linux. So this PR now just updates the documented public APIs.

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Internal previews

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docs/core/diagnostics/microsoft-diagnostics-netcore-client.md	Microsoft.Diagnostics.NETCore.Client API