[mlir][nvgpu] Simplify TMA IR generation (#87153)

This PR add `TmaDescriptorBuilder` 
- class simplifies TMA generation.
- Makes the code ready to support various Tma configurations 
   - removes strings and use the enums from `mlir.nvgpu.ENUMs`.
- Example "swizzle = swizzle_128b, l2promo=none, oob=zero,
interleave=none" to enums in `mlir.nvgpu` dialects.
- Enums have string equivalent that are used during the IR writing and
generation (see `TmaDescriptorBuilder::tensormap_descriptor_ty`).
- Improves readability and abstracts out TMA descriptor builders in
reusable component.

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Co-authored-by: Manish Gupta <manigupta@google.com>