Simplify the JsonTempDataSerializer

[dariatiurina]

Simplify the JsonTempDataSerializer

Summary

Simplifies the JsonTempDataSerializer by storing type information alongside each value, eliminating the need for heuristic type inference during deserialization. This removes the source-generated JsonTempDataSerializerContext and replaces hand-written per-type deserialization logic with a direct
JsonSerializer.Deserialize call using the stored type.

Changes

• Changes the internal TempData dictionary type from IDictionary<string, object?> to IDictionary<string, (object? Value, Type? Type)> so values carry their original type through the pipeline.
• Replaces the serialization format: each value is now stored as { "type": "<type-fullname>", "value": <json> } instead of a raw JSON value.
• Removes JsonTempDataSerializerContext (source-generated context with ~30 [JsonSerializable] attributes) — no longer needed since the type is stored explicitly.
• Removes heuristic deserialization methods (DeserializeElement, DeserializeString, DeserializeArray, DeserializeObject, GetArrayTypeInfo, GetStringType) that inferred types from JsonValueKind.
• Simplifies CanSerialize to use a static HashSet<Type> of supported types.
• Normalizes ICollection<T> types (e.g., List<T>, HashSet<T>) to T[] during serialization.
• Updates ITempDataProvider, ITempDataSerializer, TempDataService, CookieTempDataProvider, SessionStorageTempDataProvider, and TempData to use the new tuple-based dictionary.

Testing

• Replaces individual per-type deserialization tests with a single parameterized RoundTrip theory covering int, bool, string, Guid, DateTime, arrays, and dictionaries.
• Adds dedicated tests for null values, enums, enum arrays, List<T> → array normalization, and HashSet<T> → array normalization.
• Expands ValidTypes coverage with additional types (string[], bool[], DateTime[], Dictionary<string,T> variants, enums, List, HashSet).

Fixes #65231