Remove some array allocations from RuntimeType.CreateInstanceImpl (#67148)

- It's commonly used with zero args; we can use Type.EmptyTypes rather than new Type[0]
- It calls GetConstructors, which internally uses ListBuilder and then resizes if the created array isn't filled, but since we don't need the correctly sized array, we can just use the ListBuilder and avoid the resize
- It creates a List and then ToArray's it, but if none of the constructors are filtered out, it's better to just use the array we built up directly.

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

@@ -3643,11 +3643,12 @@ private void CreateInstanceCheckThis()
             }
             else
             {
-                ConstructorInfo[] candidates = GetConstructors(bindingAttr);
-                List<MethodBase> matches = new List<MethodBase>(candidates.Length);
+                ListBuilder<ConstructorInfo> candidates = GetConstructorCandidates(null, bindingAttr, CallingConventions.Any, null, false);
+                MethodBase[] cons = new MethodBase[candidates.Count];
+                int consCount = 0;
 
                 // We cannot use Type.GetTypeArray here because some of the args might be null
-                Type[] argsType = new Type[args.Length];
+                Type[] argsType = args.Length != 0 ? new Type[args.Length] : EmptyTypes;
                 for (int i = 0; i < args.Length; i++)
                 {
                     if (args[i] is object arg)
@@ -3656,18 +3657,23 @@ private void CreateInstanceCheckThis()
                     }
                 }
 
-                for (int i = 0; i < candidates.Length; i++)
+                for (int i = 0; i < candidates.Count; i++)
                 {
                     if (FilterApplyConstructorInfo((RuntimeConstructorInfo)candidates[i], bindingAttr, CallingConventions.Any, argsType))
-                        matches.Add(candidates[i]);
+                    {
+                        cons[consCount++] = candidates[i];
+                    }
                 }
 
-                if (matches.Count == 0)
+                if (consCount == 0)
                 {
                     throw new MissingMethodException(SR.Format(SR.MissingConstructor_Name, FullName));
                 }
 
-                MethodBase[] cons = matches.ToArray();
+                if (consCount != cons.Length)
+                {
+                    Array.Resize(ref cons, consCount);
+                }
 
                 MethodBase? invokeMethod;
                 object? state = null;