Add mesh shader support: Remove inactive built-in inputs if not used
Add mesh shader support: Remove inactive built-in inputs if not used

Add the processing for mesh shader, removing inactive built-in inputs if
they are not used. Previously, this was not added because the processing
seems useless. In fact, ADCE will not remove such inputs as expected
because later passes could generate such inactive inputs while ADCE has
already been run. See https://github.com/GPUOpen-Drivers/llpc/pull/1958.

GPUOpen-Drivers/llpc,GPUOpen-Drivers/llpc,GPUOpen-Drivers/llpc,GPUOpen-Drivers/llpc,GPUOpen-Drivers/llpc