More recent GCC versions (e.g. 12.2, 13.1) report that the argument to
`new[]` in the `Init` methods exceeds the maximum object size,
seemingly related to the negative range of the widened `int`.
Use an unsigned type to avoid the warning and propagate the signedness
change to other uses of the `num_elements` member.
Fixes https://github.com/KhronosGroup/OpenCL-CTS/issues/1582
Signed-off-by: Sven van Haastregt <sven.vanhaastregt@arm.com>
c8061ab21a