Fix regresion in FSR tests

Fix regresion in FSR tests

FSR tests were recently repeated few times - for pipeline libraries
and for secondary command buffers in dynamic rendering cases. As a
result there were cases where delayed group creation with
createChildren had another nested call to createChildren. This CL
modifies code to use only tow delayed group creation calls - for
renderpass2 and dynamic_rendering sub-groups.

Components: Vulkan

VK-GL-CTS issue: 3760

Affects:
dEQP-VK.fragment_shading_rate.*

Change-Id: If8da1532c0c924ef812ab055de4c71c5b9ba86b4