Refactor TagDescription and HtmlDslGenerator for Attribute Lookup

- Updated the AttributeLookup method in TagDescription to utilize a pre-defined AttributeLookupTable for improved performance and maintainability.
- Removed the previous method of dynamically constructing attribute lookups via reflection.
- Introduced a new method in HtmlDslGenerator to generate the AttributeLookupTable, ensuring a clear separation of concerns.
- Enhanced the generated output for attribute lookups, including default attributes for unknown elements.
- Adjusted related tests to accommodate the new structure and ensure correctness of generated files.

Author: EamonNerbonne