Overallocations of WhereListIterator in DependencyWalker.CreateGraphNode

[jebriede]

The DependencyWalker uses a LINQ Where in the CreateGraphNode method on a hot code path and the result is a large amount of WhereListIterators being allocated.

 Name                                                                                                                                 	Inc %	          Inc
 Type WhereListIterator`1[NuGet.LibraryModel.LibraryDependency]                                                                      	  0.6	   58,290,408
+ clr!?                                                                                                                              	  0.6	   58,290,408
 + system.core.ni!?                                                                                                                  	  0.6	   58,290,408
  + nuget.dependencyresolver.core!NuGet.DependencyResolver.RemoteDependencyWalker+<CreateGraphNode>d__3.MoveNext()                   	  0.6	   52,176,240
  |+ mscorlib.ni!System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1[System.__Canon].Start[System.__Canon](System.__Canon ByRef)	  0.6	   52,176,240
  | + nuget.dependencyresolver.core!RemoteDependencyWalker.CreateGraphNode                                                           	  0.6	   52,176,240