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

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

For example, an insert

  %0 = vector.insert %arg0, %arg1[3 : i32] : f32 into vector<4xf32>

becomes

  %0 = llvm.mlir.constant(3 : i32) : !llvm.i32
  %1 = llvm.insertelement %arg0, %arg1[%0 : !llvm.i32] : !llvm<"<4 x float>">

A more elaborate example, inserting an element in a higher dimension
vector

  %0 = vector.insert %arg0, %arg1[3 : i32, 7 : i32, 15 : i32] : f32 into vector<4x8x16xf32>

becomes

  %0 = llvm.extractvalue %arg1[3 : i32, 7 : i32] : !llvm<"[4 x [8 x <16 x float>]]">
  %1 = llvm.mlir.constant(15 : i32) : !llvm.i32
  %2 = llvm.insertelement %arg0, %0[%1 : !llvm.i32] : !llvm<"<16 x float>">
  %3 = llvm.insertvalue %2, %arg1[3 : i32, 7 : i32] : !llvm<"[4 x [8 x <16 x float>]]">

PiperOrigin-RevId: 284882443