vkr: add allow_vk_wait_syncs capset

Merged Yiwei Zhang requested to merge zzyiwei/virglrenderer:capset-feedback into master

The main purpose is to unblock mesa/mesa!16731 (merged).

When the client simulate fence or timeline semaphores with coherent memory, after the memory bits get fliped by the device, the real fence/sem signal operation are followed but the gap is variable and can let the theoretical racing happen in practice on some host gpu drivers. This capset is introduced to allow the client to fill the gap between the updated feedback and the actual signal operation.

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