venus: query experimental features in one call
It is simpler. But I mainly want to work around
../src/virtio/vulkan/vn_cs.h:173:4: error: argument 1 null where non-null expected [-Werror=nonnull]
173 | memcpy(val, dec->cur, val_size);
We trust virglrenderer and it never instructs the decoder to memcpy to pData when it is NULL. The compiler does not know however. A proper fix will be to generate
if (!pData)
unreachable();
to help the compiler.
/cc @zzyiwei