Make SkiaVulkanPipeline go through RenderThread to get VulkanManger.

Previously the pipeline held a referance to the VulkanManager on
the RenderThread. However if the RenderThread ever deleted or
recreated its VulkanManager the pipline would not update its
reference and cause crashes when accessed. This change makes it
so the pipeline always goes through the RenderThread to get the
VulkanManager.

Test: Manual build and running on phone
Bug: b/184287126, b/183289296
Change-Id: I52b37d0aa85b553e358285fa3654c2169971ffde