Refactor tests to use _All_True model types throughout
Replaced all usages of legacy test model types (e.g., TestOrder, TestOrderItem, SharedTag, etc.) with new, feature-complete _All_True variants across SignalR test infrastructure, data sources, and service handlers. Updated all generic constraints, method signatures, and test data to use the new types. Added SharedTestBaseModels.cs and SharedTestOrderModels.cs to define abstract bases and concrete _All_True models with full serialization attributes. This enables more thorough and realistic serialization/deserialization testing and future extensibility.
- Introduced a high-performance, reusable "chain" API for JSON deserialization and object population, enabling parsed JSON to be reused for multiple deserializations without reparsing. Exposed via new extension methods and interfaces (`IDeserializeChain<T>`, `IPopulateChain`).
- Added comprehensive infrastructure for serializing and deserializing .NET Expression trees to a universal DTO (`AcExpressionNode`), with full round-trip support and robust handling of constants, closures, and queryable expressions.
- Centralized all property accessor and expression utilities in `AcSerializerCommon` to avoid duplication and improve maintainability.
- Enhanced both JSON and binary serializers to support Expression and IQueryable types, with automatic conversion to/from `AcExpressionNode`.
- Refactored type metadata and property accessor logic for performance and code reuse.
- Added extensive unit tests for the new chain API and expression serialization, and reorganized test models and namespaces for clarity.
- Improved logging, error handling, and test infrastructure.
- Misc: Added settings for local builds, updated project files, and cleaned up obsolete code.
Loretta