Fix ConcurrentDictionary test by rooting members accessed via reflection (#81957)

Author: stephentoub

src/libraries/System.Collections.Concurrent/tests/System.Collections.Concurrent.Tests.csproj

@@ -5,6 +5,9 @@
     <TargetFramework>$(NetCoreAppCurrent)</TargetFramework>
     <DebuggerSupport Condition="'$(DebuggerSupport)' == '' and '$(TargetOS)' == 'browser'">true</DebuggerSupport>
   </PropertyGroup>
+  <ItemGroup>
+    <RdXmlFile Include="default.rd.xml" />
+  </ItemGroup>
   <ItemGroup>
     <Compile Include="$(CoreLibSharedDir)System\Collections\Concurrent\IProducerConsumerCollectionDebugView.cs"
              Link="System\Collections\Concurrent\IProducerConsumerCollectionDebugView.cs" />

src/libraries/System.Collections.Concurrent/tests/default.rd.xml

@@ -0,0 +1,8 @@
+<Directives>
+  <Application>
+    <Assembly Name="System.Collections.Concurrent">
+      <Type Name="System.Collections.Concurrent.ConcurrentDictionary`2[[System.String, System.Private.CoreLib],[System.String, System.Private.CoreLib]]" Dynamic="Required All" />
+      <Type Name="System.Collections.Concurrent.ConcurrentDictionary`2[[System.String, System.Private.CoreLib],[System.String, System.Private.CoreLib]]+Tables" Dynamic="Required All" />
+    </Assembly>
+  </Application>
+</Directives>