[cDAC] Ensure mt created (#129114)

Before checking the dict of MTs when not coming directly from a
constructed TypeHandle, ensure that the MethodTable is created.

Author: rcj1

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/RuntimeTypeSystem_1.cs

@@ -1345,7 +1345,7 @@ private bool RequiresInstArgMethodTable(MethodDesc methodDesc)
         if (methodDesc.IsStatic)
             return true;
 
-        MethodTable mt = _methodTables[methodDesc.MethodTable];
+        MethodTable mt = GetOrCreateMethodTable(methodDesc);
         if (mt.Flags.IsValueType)
             return true;
 
@@ -1385,7 +1385,7 @@ private bool IsSharedByGenericInstantiations(MethodDesc methodDesc)
         }
 
         // Check class-level sharing: canonical MethodTable with generic instantiation
-        MethodTable mt = _methodTables[methodDesc.MethodTable];
+        MethodTable mt = GetOrCreateMethodTable(methodDesc);
         return mt.IsCanonMT && mt.Flags.HasInstantiation;
     }
 
@@ -1397,7 +1397,7 @@ private bool IsAbstract(MethodDesc methodDesc)
         if (EcmaMetadataUtils.GetRowId(token) == 0)
             return false;
 
-        TargetPointer modulePtr = _methodTables[methodDesc.MethodTable].Module;
+        TargetPointer modulePtr = GetOrCreateMethodTable(methodDesc).Module;
         ModuleHandle moduleHandle = _target.Contracts.Loader.GetModuleHandleFromModulePtr(modulePtr);
         MetadataReader? mdReader = _target.Contracts.EcmaMetadata.GetMetadata(moduleHandle);
         if (mdReader is null)