venus: avoid client allocators for ring internals

What does this MR do and why?

venus: avoid client allocators for ring internals

There're many cases in which the ring submissions must succeed. We don't worry about real oom since things would fail earlier. For simulated oom from random intentional allocs, there isn't robust way to fail those must succeeds. e.g. the commands that don't have return codes or valid error return struct defaults. So real oom propagation is still at best effort.

Cc: mesa-stable

Test:

• dEQP-VK.api.object_management.alloc_callback_fail.*
• dEQP-VK.*simulate_oom*