[SM6.9] Handle native vector operations in DXIL Convergence Mark pass

**Description**
DXC propagates convergence from the convergent operation up through the argument dominators. This enables that pass to propagate convergence upward for vector arguments.

**Additional Context**
Draft implementation: https://github.com/pow2clk/DirectXShaderCompiler/commit/ccc15baeaa8eca90de6a4da5ea3dad8d7e535759