Predicate<T> vs. Action<T, Boolean>

The System.Predicate<T> delegate type is duplicative with System.Function<T, Boolean>, as illustrated by comparing System.Collections.Generic.List.FindAll() with System.Linq.Enumerable.Where(). Some usage guidance would be helpful.

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* ID: 1a8d0749-53d0-c82d-ad93-4e0f23c9a4ae
* Version Independent ID: 8ab2952a-7581-404f-a385-bce7656413a3
* Content: [Predicate<T> Delegate (System)](https://docs.microsoft.com/en-us/dotnet/api/system.predicate-1?view=netframework-4.7.2)
* Content Source: [xml/System/Predicate`1.xml](https://github.com/dotnet/dotnet-api-docs/blob/master/xml/System/Predicate`1.xml)
* Product: **dotnet-api**
* GitHub Login: @rpetrusha
* Microsoft Alias: **ronpet**