fix duplicate registration of named tuples

[honda-tatsuya]

Example

using MessagePack;
using System.Collections.Generic;

[MessagePackObject]
public class Test
{
    [Key(0)] public Dictionary<((int A, int B) C, (int D, int E) F), ((int G, int H) I, (int J, int K) L)> Hoge;
    [Key(1)] public ((int M, int N) O, (int P, int Q) R)[,] Fuga;
}

Before

        static GeneratedResolverGetFormatterHelper()
        {
            lookup = new global::System.Collections.Generic.Dictionary<global::System.Type, int>(12)
            {
                { typeof(((int A, int B) C, (int D, int E) F)), 0 },
                { typeof(((int G, int H) I, (int J, int K) L)), 1 },
                { typeof(((int M, int N) O, (int P, int Q) R)), 2 },
                { typeof(((int M, int N) O, (int P, int Q) R)[,]), 3 },
                { typeof((int A, int B)), 4 },
                { typeof((int D, int E)), 5 },
                { typeof((int G, int H)), 6 },
                { typeof((int J, int K)), 7 },
                { typeof((int M, int N)), 8 },
                { typeof((int P, int Q)), 9 },
                { typeof(global::System.Collections.Generic.Dictionary<((int A, int B) C, (int D, int E) F), ((int G, int H) I, (int J, int K) L)>), 10 },
                { typeof(global::Test), 11 },
            };
        }

This is runtime error
ArgumentException: An item with the same key has already been added. Key: System.ValueTuple`2[System.Int32,System.Int32]

After

        static GeneratedResolverGetFormatterHelper()
        {
            lookup = new global::System.Collections.Generic.Dictionary<global::System.Type, int>(5)
            {
                { typeof(((int, int), (int, int))), 0 },
                { typeof(((int, int), (int, int))[,]), 1 },
                { typeof((int, int)), 2 },
                { typeof(global::System.Collections.Generic.Dictionary<((int, int), (int, int)), ((int, int), (int, int))>), 3 },
                { typeof(global::Test), 4 },
            };
        }

[neuecc]

thanks, it seems good.
approve to merge.

[AArnott]

@honda-tatsuya Thanks for your contribution. Can you please review the test failures and address them?

[github-actions]

This pull request is stale because it has been open 90 days with no activity. Remove stale label or comment or this will be closed in 5 days.

[honda-tatsuya]

@AArnott I fixed it. sorry for the delay.