Add list of tests for each fraction of CTS parallel run

Add list of tests for each fraction of CTS parallel run

The tests may be split in groups for parallel execution
using commandline deqp-fraction parameter.
This commit adds possibility to perform a list of tests
for each such fraction.
To achieve this - user must use parameter
deqp-fraction-mandatory-caselist-file defining a file with
a list of tests. File vk-fraction-mandatory-tests.txt
defines a list of mandatory tests when parallel execution
is applied.

Components: Vulkan Framework

VK-GL-CTS issue: 1897

Change-Id: I684eb07c24bbf3aeaf3386f205658dfe07b9fe25