[dotnet] Copy the app.config file to the app bundle.

[rolfbjarne]

Fixes this monotouch-test failure:

MonoTouchFixtures.ConfigTest
    [FAIL] Existence :   existence
       Expected: True
       But was:  False
           at MonoTouchFixtures.ConfigTest.Existence() in /Users/rolf/work/maccore/squashed-onedotnet/xamarin-macios/tests/monotouch-test/mono/ConfigTest.cs:line 19

[monojenkins]

Build failure
✅ Provisioning succeeded
✅ Build succeeded
✅ API Diff (from stable)
✅ API Diff (from PR only) (no change)
✅ Generator Diff (no change)
🔥 Test run failed 🔥

Test results

2 tests failed, 88 tests passed.

Failed tests

• interdependent-binding-projects/iOS Unified 64-bits - simulator/Debug [dotnet]: BuildFailure (Harness exception for 'interdependent-binding-projects': System.IO.DirectoryNotFoundException: Could not find a part of the path "/Users/builder/jenkins/workspace/xamarin-macios-pr-builder/tests/external/Touch.Unit/Touch.Client/dotnet/iOS/Touch.Client-iOS.dotnet.csproj".
  at System.IO.FileStream..ctor (System.String path, System.IO.FileMode mode, System.IO.FileAccess access, System.IO.FileShare share, System.Int32 bufferSize, System.Boolean anonymous, System.IO.FileOptions options) [0x0015e] in /Users/builder/jenkins/workspace/build-package-osx-mono/2020-02/external/bockbuild/builds/mono-x64/mcs/class/corlib/System.IO/FileStream.cs:223
  at System.IO.FileStream..ctor (System.String path, System.IO.FileMode mode, System.IO.FileAccess access, System.IO.FileShare share, System.Int32 bufferSize, System.Boolean isAsync, System.Boolean anonymous) [0x00000] in /Users/builder/jenkins/workspace/build-package-osx-mono/2020-02/external/bockbuild/builds/mono-x64/mcs/class/corlib/System.IO/FileStream.cs:149
  at System.IO.FileStream..ctor (System.String path, System.IO.FileMode mode, System.IO.FileAccess access) [0x00000] in /Users/builder/jenkins/workspace/build-package-osx-mono/2020-02/external/bockbuild/builds/mono-x64/mcs/class/corlib/System.IO/FileStream.cs:86
  at (wrapper remoting-invoke-with-check) System.IO.FileStream..ctor(string,System.IO.FileMode,System.IO.FileAccess)
  at Microsoft.DotNet.XHarness.iOS.Shared.Utilities.PListExtensions.LoadWithoutNetworkAccess (System.Xml.XmlDocument doc, System.String filename) [0x00001] in /Users/builder/jenkins/workspace/xamarin-macios-pr-builder/tests/xharness/Microsoft.DotNet.XHarness.iOS.Shared/Utilities/PlistExtensions.cs:17
  at Microsoft.DotNet.XHarness.iOS.Shared.TestProject.CreateCopyAsync (Microsoft.DotNet.XHarness.iOS.Shared.Logging.ILog log, Microsoft.DotNet.XHarness.iOS.Shared.Execution.IProcessManager processManager, Microsoft.DotNet.XHarness.iOS.Shared.Tasks.ITestTask test, System.String rootDirectory, System.Collections.Generic.Dictionary2[TKey,TValue] allProjectReferences) [0x0010c] in /Users/builder/jenkins/workspace/xamarin-macios-pr-builder/tests/xharness/Microsoft.DotNet.XHarness.iOS.Shared/TestProject.cs:98 at Microsoft.DotNet.XHarness.iOS.Shared.TestProject.CreateCopyAsync (Microsoft.DotNet.XHarness.iOS.Shared.Logging.ILog log, Microsoft.DotNet.XHarness.iOS.Shared.Execution.IProcessManager processManager, Microsoft.DotNet.XHarness.iOS.Shared.Tasks.ITestTask test, System.String rootDirectory, System.Collections.Generic.Dictionary2[TKey,TValue] allProjectReferences) [0x00811] in /Users/builder/jenkins/workspace/xamarin-macios-pr-builder/tests/xharness/Microsoft.DotNet.XHarness.iOS.Shared/TestProject.cs:168
  at Microsoft.DotNet.XHarness.iOS.Shared.Tasks.TestTasks.RunInternalAsync () [0x00117] in /Users/builder/jenkins/workspace/xamarin-macios-pr-builder/tests/xharness/Microsoft.DotNet.XHarness.iOS.Shared/Tasks/TestTask.cs:274 )
• monotouch-test/watchOS 32-bits - simulator/Debug: Failed Known issue: HE0038)

[mandel-macaque]

And again, the independent bindings error has happened in other PRs, such as #9470

[rolfbjarne]

Test failures are unrelated

• interdependent-binding-tests: [xharness] Process '$(RootTestsDirectory)' before bailing due to any other variables when resolving paths in project files. #9467.
• monotouch-test/watchOS 32-bit: https://github.com/xamarin/maccore/issues/581