tu: Enable VK_EXT_shader_stencil_export

This passes the grand total of 3 CTS tests (2 actually enabled due to
missing D32_SFLOAT_S8_UINT support) under
dEQP-VK.pipeline.shader_stencil_export.*

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5936>
3 files changed