[VectorOps] Add lowering of vector.shuffle to LLVM IR

For example, a shuffle

%1 = vector.shuffle %arg0, %arg1 [0 : i32, 1 : i32] : vector<2xf32>, vector<2xf32>

becomes a direct LLVM shuffle

0 = llvm.shufflevector %arg0, %arg1 [0 : i32, 1 : i32] : !llvm<"<2 x float>">, !llvm<"<2 x float>">

but

%1 = vector.shuffle %a, %b[1 : i32, 0 : i32, 2: i32] : vector<1x4xf32>, vector<2x4xf32>

becomes the more elaborate (note the index permutation that drives
argument selection for the extract operations)

%0 = llvm.mlir.undef : !llvm<"[3 x <4 x float>]">
%1 = llvm.extractvalue %arg1[0] : !llvm<"[2 x <4 x float>]">
%2 = llvm.insertvalue %1, %0[0] : !llvm<"[3 x <4 x float>]">
%3 = llvm.extractvalue %arg0[0] : !llvm<"[1 x <4 x float>]">
%4 = llvm.insertvalue %3, %2[1] : !llvm<"[3 x <4 x float>]">
%5 = llvm.extractvalue %arg1[1] : !llvm<"[2 x <4 x float>]">
%6 = llvm.insertvalue %5, %4[2] : !llvm<"[3 x <4 x float>]">

PiperOrigin-RevId: 285268164