Add tests for VK_KHR_shader_atomic_int64

Add tests for VK_KHR_shader_atomic_int64

Add new test cases for 64 bit int atomic operations
to existing glsl.atomic_operations tests

New tests:
dEQP-VK.glsl.atomic_operations.*signed64bit*
dEQP-VK.glsl.atomic_operations.*unsigned64bit*

Affected tests:
dEQP-VK.glsl.atomic_operations.*

Components: Vulkan, Framework, Scripts

VK-GL-CTS issue:1172

Change-Id: If7e6871cc209b2086e087e0dd6c764cb8bd98a4b
(cherry picked from commit 80926e1393d1a3de407b9279162056fa0a53822e)