[Triton-MLIR][OPTIMIZER] Cleaned up swizzling (#869)

Swizzling is no longer implemented as a separate pass. It is instead
done in a specialized constructor of SharedEncodingAttr, and tested via
google tests instead of triton-opt + filecheck.

In the future we may want to implement it as a pass again once we have
an additional dialect between TritonGPU and LLVM.

python/src/triton.cc

@@ -1264,10 +1264,6 @@ void init_triton_ir(py::module &&m) {
            [](mlir::PassManager &self) {
              self.addPass(mlir::createTritonGPUCombineOpsPass());
            })
-      .def("add_triton_gpu_swizzle_pass",
-           [](mlir::PassManager &self) {
-             self.addPass(mlir::createTritonGPUSwizzlePass());
-           })
       .def("add_triton_gpu_to_llvm",
            [](mlir::PassManager &self) {
              self.addPass(mlir::triton::createConvertTritonGPUToLLVMPass());