Plumb support for rendering A8 in Vulkan

VulkanSurface:
- update LOG_TAG
- allow no dataspace + A8
- assign a vkPixelFormat for A8

VulkanManager: use a more descriptive LOG_TAG

Bug: 193170859
Test: TODO

Change-Id: If447c2c393b4f17b718083a77cdd29870fb1cc50
2 files changed