glsl: Add tracking for elements of an array-of-arrays that have been accessed

glsl: Add tracking for elements of an array-of-arrays that have been accessed

If there's a better way to provide access to ir_array_refcount_entry
private members to the test functions, I am very interested to know
about it.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Cc: Francisco Jerez <currojerez@riseup.net>
Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>