08545e8516
This is the 1st PR of [Mesh sharding RFC](https://discourse.llvm.org/t/open-mlir-meeting-9-28-2023-rfc-sharding-framework-design-for-device-mesh/73695), includes Includes: - mesh.cluster op - mesh.shard op (the mesh.annotate op in the RFC slides, the name is modified a bit from @stellaraccident 's advice, which I think might be a bit more concise) - MeshSharding attribute