vkr: further cleanup after mandating server config
- 1-6 commits are mainly refactorings and removing legacy code path
- legacy vkr renderer interface backing virglrenderer is no longer needed
- vkr behind the server has mandated async fence cb
- 7-8 commits get rid of virgl_context from vkr
- 9-13 commits get rid of virgl_resource from vkr
- 14-17 commits are further optimizations of vkr context interfaces
Edited by Yiwei Zhang