Fixes: dotnet#8797

Here are two cases `TrimMode=full` can break applications:

* `$(AndroidHttpClientHandlerType)` set to a custom type

* Custom views (Android `.xml`) that are not referenced in C# code

In the `MarkJavaObjects` trimmer step we can preserve both of these
cases by:

* Passing in `$(AndroidHttpClientHandlerType)`, preserve the public,
  parameterless constructor of the type

* Pass in `$(_CustomViewMapFile)`, preserve `IJavaObject` types if
  they are found in the map file