tu: Support VK_FORMAT_FEATURE_BLIT_SRC_BIT for texture-only formats
Also fix some bugs noticed while trying to write dEQP tests for this case. This fixes a bunch more dEQP-VK.api.format_properties
tests.
I have a WIP branch at https://github.com/cwabbott0/VK-GL-CTS/commits/blit-compressed-src to test blitting from compressed textures, but I hit what seem like precision issues as the differences in the result image are tiny. I think dEQP expects lower precision when sampling from compressed formats, but I got lost in the dEQP maze when trying to figure out what precision to use.