Several subgroup features aren't tested

Here's a (possibly non-exhaustive) list of built-in functions that aren't tested:

* `get_kernel_sub_group_count_for_ndrange`
* `get_kernel_max_sub_group_size_for_ndrange`

A few other features aren't tested at all:

* `memory_scope_sub_group`

Start by locating the existing tests or entry points for get_kernel_sub_group_count_for_ndrange and get_kernel_max_sub_group_size_for_ndrange. Also find how memory_scope_sub_group is exercised. Done means coverage exists for both listed built-in functions and the subgroup memory scope feature.

Written by the indexing model from the issue text.