[Tests] Add missing nuget. (#15313)

Tests work because other tests do use the nugets and gets picked up by
the runner. Yet, if we execute this projects witjout others, the tests
will fail when trying to use the nunit2 format.

Co-authored-by: Rolf Bjarne Kvinge <rolf@xamarin.com>

tests/generator/generator-tests.csproj

@@ -32,6 +32,7 @@
     <Reference Include="System.Xml" />
     <PackageReference Include="NUnit" Version="3.12.0" />
     <PackageReference Include="NUnit.ConsoleRunner" Version="3.11.1" />
+    <PackageReference Include="NUnit.Extension.NUnitV2ResultWriter" Version="3.6.0" />
     <PackageReference Include="Mono.Cecil" Version="0.11.4" />
     <PackageReference Include="MSBuild.StructuredLogger" Version="2.1.500" />
   </ItemGroup>
@@ -81,4 +82,4 @@
     </ProjectReference>
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
-</Project>
+</Project>

tests/mmptest/mmptest.csproj

@@ -35,6 +35,7 @@
     <Reference Include="System.Xml" />
     <PackageReference Include="NUnit" Version="3.12.0" />
     <PackageReference Include="NUnit.ConsoleRunner" Version="3.11.1" />
+    <PackageReference Include="NUnit.Extension.NUnitV2ResultWriter" Version="3.6.0" />
     <Reference Include="mmp">
       <Aliases>global,mmp</Aliases>
       <HintPath Condition="$(TESTS_USE_SYSTEM) == ''">..\..\_mac-build\Library\Frameworks\Xamarin.Mac.framework\Versions\git\lib\mmp\mmp.exe</HintPath>

tests/mtouch/mtouchtests.csproj

@@ -26,7 +26,8 @@
     <Reference Include="Mono.Posix" />
     <Reference Include="System.Xml" />
     <PackageReference Include="NUnit" Version="3.12.0" />
-    <PackageReference Include="NUnit.ConsoleRunner" Version="3.11.1" />
+    <PackageReference Include="NUnit.ConsoleRunner" Version="3.12.0" />
+    <PackageReference Include="NUnit.Extension.NUnitV2ResultWriter" Version="3.6.0" />
     <PackageReference Include="MSBuild.StructuredLogger" Version="2.1.500" />
     <Reference Include="Mono.Cecil">
       <HintPath>..\..\builds\mono-ios-sdk-destdir\ios-bcl\monotouch_tools\Mono.Cecil.dll</HintPath>

tools/nunit3-console-3.12.0

@@ -0,0 +1,10 @@
+#!/bin/bash -eu
+
+# This makes it so that stack traces have source code location
+if test -z "${MONO_ENV_OPTIONS:-}"; then
+	export MONO_ENV_OPTIONS=--debug
+fi
+
+TOP="$(cd "$(dirname "$0")/.." && pwd)"
+
+exec mono --debug "$TOP"/packages/nunit.consolerunner/3.12.0/tools/nunit3-console.exe "$@"