Introduces a polymorphic describe() method to BaseOperator that enables runtime introspection of kernel configurations through a unified interface.
Key changes:
* Add virtual describe() method to BaseOperator returning Description objects
* Implement describe() in 6 device operation classes (conv fwd/bwd variants)
* Create conv_describe.hpp with factory function for ConvDescription
* Extract type definitions to conv_types.hpp to resolve circular dependencies
* Add InstanceStringDescription for kernels without full ConvDescription support
Other Improvements:
* Update tests to use describe() instead of GetInstanceString()
* Remove circular dependency include from conv_traits.hpp
* Add ODD_C to ConvFwdSpecialization enum and fix OddC mapping
* Replace silent fallback in conv_layout() with compile-time error
This provides a foundation for runtime kernel introspection and better tooling support for analyzing and debugging kernel configurations.
