Make it possible for arrays to have default-implemented methods (dotnet#96672)

Within the managed type system, the array types are special. When asking question about virtual/interface methods implemented by arrays, one needs to switch from the array type (that doesn't have any virtual methods as far as the type system in concerned) to the `Array<T>` type from corelib (that has the methods).

The `GetClosestDefType` API is the API that does this transformation. We were not consistent enough in using it and it didn't work for default methods.

In dotnet#95830, arrays are going to get a default interface method (the implementation of `IList<T>.System.Collections.Generic.IReadOnlyList<T>.get_Item` which is `virtual final` but still a new slot).

Author: MichalStrehovsky

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/EETypeNode.cs

@@ -531,7 +531,7 @@ public sealed override IEnumerable<CombinedDependencyListEntry> GetConditionalSt
                                 if (!isStaticInterfaceMethod && defaultIntfMethod.IsCanonicalMethod(CanonicalFormKind.Any))
                                 {
                                     // Canonical instance default methods need to go through a thunk that adds the right generic context
-                                    defaultIntfMethod = factory.TypeSystemContext.GetDefaultInterfaceMethodImplementationThunk(defaultIntfMethod, _type.ConvertToCanonForm(CanonicalFormKind.Specific), providingInterfaceDefinitionType);
+                                    defaultIntfMethod = factory.TypeSystemContext.GetDefaultInterfaceMethodImplementationThunk(defaultIntfMethod, defType.ConvertToCanonForm(CanonicalFormKind.Specific), providingInterfaceDefinitionType);
                                 }
                                 result.Add(new CombinedDependencyListEntry(factory.MethodEntrypoint(defaultIntfMethod), factory.VirtualMethodUse(interfaceMethod), "Interface method"));
 

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/SealedVTableNode.cs

@@ -216,9 +216,11 @@ public override ObjectData GetData(NodeFactory factory, bool relocsOnly)
 
             if (BuildSealedVTableSlots(factory, relocsOnly))
             {
+                DefType defType = _type.GetClosestDefType();
+
                 for (int i = 0; i < _sealedVTableEntries.Count; i++)
                 {
-                    IMethodNode relocTarget = _sealedVTableEntries[i].GetTarget(factory, _type);
+                    IMethodNode relocTarget = _sealedVTableEntries[i].GetTarget(factory, defType);
 
                     if (factory.Target.SupportsRelativePointers)
                         objData.EmitReloc(relocTarget, RelocType.IMAGE_REL_BASED_RELPTR32);