Add to docs: AssemblyLoadContext is GC.Pinned

[dave-yotta]

I've recently hit a problem with (catastrophic) file handle leaks due to non unloaded assemblies. The docs are clear that unloading happens after all references into the loaded assemblies are collected - however my subclass of the AssemblyLoadContext was storing such references. It was disposed/out of scope, but it turns out the implementation keeps a strong GCHandle to the AssemblyLoadContext, so my references despite being out of scope are not collected.

Please can we add to the bulletpoints at the top of the page something along the lines of:

 - The runtime keeps a strong GCHandle to the AssemblyLoadContext and will not be collected by the GC, so you will need to remove any references on the `AssemblyLoadContext` you have subclassed into loaded assemblies before the `Unload` will complete.

Thanks - related issue over here: dotnet/runtime#44679

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Document Details

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• ID: f3283764-f15a-fa5f-5106-6f294c780f7b
• Version Independent ID: b03cedce-9074-9686-0b31-045b2b4c862d
• Content: How to use and debug assembly unloadability in .NET Core
• Content Source: docs/standard/assembly/unloadability.md
• Product: dotnet-fundamentals
• GitHub Login: @janvorli
• Microsoft Alias: janvorli

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Associated WorkItem - 562695

[PathogenDavid]

It's worth noting that a strong GCHandle isn't the same thing as a pinned one, the word "pinned" should not be used here.

[dave-yotta]

Thanks - edited the description :)