Add missing writes to PointSize in subgroups tests

Add missing writes to PointSize in subgroups tests

When shaderTessellationAndGeometryPointSize is enabled the PointSize
builtin is undefined unless it is written to in the last vertex
processing phase so propagate the write through all vertex stages.

Affects:
dEQP-VK.subgroups.*

Components: Vulkan

VK-GL-CTS issue: 2404

Change-Id: Id8ffe8401c0a69d1e13847d168bafcec7e3c7a52
(cherry picked from commit 75f9abc189d4bef82d9496f55284c382b3b7a43f)