Support Managed Threadpool Diagnostics

[tommcdon]

The goal is to maintain parity with existing diagnostics for the native thread pool. Currently the concrete work for this item is:

• Make NativeRuntimeEventSource.cs as a general way of sending runtime events from managed side, as opposed to what it is now
• Make sure the events being fired from the managed ThreadPool is being fired correctly.
• Fix EventListener deadlock that can occur as part of enabling managed threadpool events through EventListener
• Make sure EventListeners can subscribe to managed threadpool events
• Test LTTng events can still get fired from managed threadpool under the Microsoft-Windows-DotNETRuntime provider

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Issue Details

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Make NativeRuntimeEventSource.cs as a general way of sending runtime events from managed side, as opposed to what it is now

Author:	tommcdon
Assignees:	-
Labels:	area-Diagnostics-coreclr
Milestone:	6.0.0

[sywhang]

#45666 fixed an issue where the managed threadpool was firing several verbose threadpool events whenever any runtime event is enabled.