Test multiple sets with dynamic offsets

Test multiple sets with dynamic offsets

This commit modifies the dynamic offset tests with two additional
strategies for grouping dynamic descriptors. Originally, these tests put
all descriptors in a single set.

Now, there is a second strategy in which every descriptor is put in a
separate set (at most 4 descriptors are used, so the tests never go over
maxBoundDescriptorSets in a conformant implementation).

A third strategy groups descriptors in arrays at binding zero, using one
set for dynamic descriptors and one set for nondynamic descriptors.

Affected and new tests:
dEQP-VK.pipeline.dynamic_offset.*

Components: Vulkan
VK-GL-CTS issue: 2248

Change-Id: I2e5d55b166f7e4424ba7ff7d6389d308da408eeb