tu: Start tracking shaders independently of pipeline

tu: Start tracking shaders independently of pipeline

We will gradually transition over users of cmd->state.pipeline and
TU_CMD_DIRTY_PIPELINE to shaders and derived state from shaders. This
just puts in place the framework to start doing that.

When importing a library with all of the shader state, we now have to
import the shaders in addition to the program, so that they are
available when we bind the pipeline.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25276>