Keep track which SBT records are needed and initialize all needed ones

Keep track which SBT records are needed and initialize all needed ones

This fixes using uninitialized memory for SBT records, when
prepareShaderBindingTable() prepares them with flags == 0.

New boolean field is added to SBT description, marked as true when
SBT is needed according to prepareShaderBindingTable()  and needs to
be copied to device memory.

Components: Vulkan

VK-GL-CTS Issue: 3598

Affects: dEQP-VK.ray_tracing_pipeline.pipeline_no_null_shaders_flag.*

Change-Id: I5a0a4f6137cece312f7474e1c47c76eb358f62a4