Avoid unordered_map for runtime datatype mapping

[LwhJesse]

Summary

Replace per-call std::unordered_map construction used for RuntimeDatatype to cute::UMMA::MXF8F6F4Format conversion in GEMM operation wrappers with a switch-based local helper.

The mapping is fixed and small, so this avoids constructing a temporary hash map during argument update while preserving the supported mappings for:

• RuntimeDatatype::kE4M3
• RuntimeDatatype::kE5M2
• RuntimeDatatype::kE3M2
• RuntimeDatatype::kE2M1

This also fixes the unsupported runtime datatype path by replacing the previous assert string expression with a real debug assertion and an explicit Status::kErrorInvalidProblem return.

Changed files

• tools/library/src/gemm_operation_3x.hpp
• tools/library/src/sparse_gemm_operation_3x.hpp
• tools/library/src/blockwise_gemm_operation_3x.hpp

Local validation

• git diff --check HEAD~1..HEAD
• Verified no remaining RuntimeDatatype std::unordered_map mapping in the touched files
• Verified the corrected debug assertion path appears once in each touched file

Full local CUTLASS builds are not practical on my machine, so I am relying on project CI and maintainer review for full validation.