Rewrite HashSet<T>'s implementation based on Dictionary<T>'s (#37180)

* Move HashSet to Corelib

* Small style cleanups in Dictionary

And factor out InsertionBehavior into its own file

* Rewrite HashSet based on Dictionary's implementation

This effectively deletes HashSet's data structure and replaces it with the one used by Dictionary, then updated for the differences (e.g. just a value rather than a key and a value).  HashSet used to have the same implementation, but Dictionary has evolved significantly and HashSet hasn't; this brings them to basic parity on implementation.

Based on perf tests, I veered away from Dictionary's implementation in a few places (e.g. a goto-based implementation in the core find method led to a significant regression for Int32-based Contains operations), and we should follow-up to understand whether Dictionary should be changed as well, or why there's a difference between the two.

Functionally, bringing over Dictionary's implementation yields a few notable changes, namely that Remove and Clear no longer invalidate enumerations.  The tests have been updated accordingly.

* Make a corresponding cleanup change to Dictionary

* Use HashSet in Corelib

* Address PR feedback

* Clean up HashSetEqualityComparer

* Port Dictionary's comparer serialization test to HashSet

* Address PR feedback

src/coreclr/src/System.Private.CoreLib/src/System/RuntimeType.CoreCLR.cs

@@ -989,7 +989,7 @@ private RuntimeType[] PopulateInterfaces(Filter filter)
                     }
                     else
                     {
-                        List<RuntimeType?> al = new List<RuntimeType?>();
+                        var al = new HashSet<RuntimeType>();
 
                         // Get all constraints
                         Type[] constraints = declaringType.GetGenericParameterConstraints();
@@ -1003,31 +1003,16 @@ private RuntimeType[] PopulateInterfaces(Filter filter)
 
                             Type[] temp = constraint.GetInterfaces();
                             for (int j = 0; j < temp.Length; j++)
-                                al.Add(temp[j] as RuntimeType);
+                                al.Add((RuntimeType)temp[j]);
                         }
 
-                        // Remove duplicates
-                        Dictionary<RuntimeType, RuntimeType> ht = new Dictionary<RuntimeType, RuntimeType>();
-                        for (int i = 0; i < al.Count; i++)
+                        // Populate list, without duplicates
+                        foreach (RuntimeType rt in al)
                         {
-                            RuntimeType constraint = al[i]!;
-                            if (!ht.ContainsKey(constraint))
-                                ht[constraint] = constraint;
-                        }
-
-                        RuntimeType[] interfaces = new RuntimeType[ht.Values.Count];
-                        ht.Values.CopyTo(interfaces, 0);
-
-                        // Populate link-list
-                        for (int i = 0; i < interfaces.Length; i++)
-                        {
-                            if (filter.RequiresStringComparison())
+                            if (!filter.RequiresStringComparison() || filter.Match(RuntimeTypeHandle.GetUtf8Name(rt)))
                             {
-                                if (!filter.Match(RuntimeTypeHandle.GetUtf8Name(interfaces[i])))
-                                    continue;
+                                list.Add(rt);
                             }
-
-                            list.Add(interfaces[i]);
                         }
                     }
 

src/libraries/System.Collections/src/Resources/Strings.resx

@@ -111,9 +111,6 @@
   <data name="Arg_BitArrayTypeUnsupported" xml:space="preserve">
     <value>Only supported array types for CopyTo on BitArrays are Boolean[], Int32[] and Byte[].</value>
   </data>
-  <data name="Arg_HSCapacityOverflow" xml:space="preserve">
-    <value>HashSet capacity is too big.</value>
-  </data>
   <data name="Arg_HTCapacityOverflow" xml:space="preserve">
     <value>Hashtable's capacity overflowed and went negative. Check load factor, capacity and the current size of the table.</value>
   </data>

src/libraries/System.Collections/src/System.Collections.csproj

@@ -11,14 +11,11 @@
   </ItemGroup>
   <ItemGroup>
     <Compile Include="System\Collections\BitArray.cs" />
-    <Compile Include="System\Collections\Generic\BitHelper.cs" />
     <Compile Include="System\Collections\Generic\CollectionExtensions.cs" />
     <Compile Include="$(CoreLibSharedDir)System\Collections\Generic\ICollectionDebugView.cs"
              Link="Common\System\Collections\Generic\ICollectionDebugView.cs" />
     <Compile Include="$(CoreLibSharedDir)System\Collections\Generic\IDictionaryDebugView.cs"
              Link="Common\System\Collections\Generic\IDictionaryDebugView.cs" />
-    <Compile Include="System\Collections\Generic\HashSet.cs" />
-    <Compile Include="System\Collections\Generic\HashSetEqualityComparer.cs" />
     <Compile Include="System\Collections\Generic\LinkedList.cs" />
     <Compile Include="System\Collections\Generic\Queue.cs" />
     <Compile Include="System\Collections\Generic\QueueDebugView.cs" />
@@ -33,6 +30,8 @@
     <!-- Shared Common -->
     <Compile Include="$(CoreLibSharedDir)System\Collections\HashHelpers.cs"
              Link="Common\System\Collections\HashHelpers.cs" />
+    <Compile Include="$(CommonPath)System\Collections\Generic\BitHelper.cs"
+             Link="Common\System\Collections\Generic\BitHelper.cs" />
     <Compile Include="$(CommonPath)System\Collections\Generic\EnumerableHelpers.cs"
              Link="Common\System\Collections\Generic\EnumerableHelpers.cs" />
   </ItemGroup>