* Fix '--msl-multi-patch-workgroup' cases where thread count exceeds data bounds
*Fix gl_PrimitiveID off by one error when computing last valid index
*Point gl_out to the last patch's data when threads exceed input data bounds
*Point patchOut to the last patch's data when threads exceed input data bounds
* Update MSL test expectations.
* Undo change to MSL multi-patch hull output bound checks
* Update MSL multi-patch test expectations.
`half` cannot be bitcasted to `float`, because the two types are not the
same size. Use an expanding cast instead.
We were already doing this for stores to the tessellation levels; why I
didn't also do this for loads is beyond me.