Add coverage for depth bias

Add coverage for depth bias

dEQP-VK didn't have coverage for depth bias testing.
This change verifies that the bias is calculated correctly
with floating-point depth format and integer depth formats.
The amber files copyrights under line_continuity have also been updated.
Updated amber commit id in fetch_sources.py.

New tests:

dEQP-VK.rasterization.depth_bias.*

Components: Vulkan

VK-GL-CTS issue: 2606

Change-Id: I82bdffef879f372e03602cd091e1675258c137ea