SPIR-V environment specification misses requirements for Work-group Collective Functions.

From https://www.khronos.org/registry/OpenCL/specs/3.0-unified/html/OpenCL_C.html#work-group-functions:
> We use the generic type name gentype to indicate the built-in data types half [69], int, uint, long [70], ulong, float or double [71] as the type for the arguments.
> ...
> gentype work_group_broadcast(gentype a, size_t local_id)

Which means that `OpGroupBroadcast` should not be allowed for OpTypeInt with Width equal to 8 or 16.

Start with the linked OpenCL C work-group functions specification and the SPIR-V environment specification's OpGroupBroadcast requirements. Confirm that 8- and 16-bit OpTypeInt operands are excluded, then verify the specification text consistently reflects that restriction.

Written by the indexing model from the issue text.