[pixels-cpp] implementation of bufferpool manager

[whzruc]

[whzruc]

The previous memory implementation was quite simple — each thread had a fixed buffer assigned for io_uring operations. As a result, if the required buffer size exceeded the preallocated amount, the program would encounter errors.

[whzruc]

[whzruc]

“If you want to support partial buffer replacement without fully unregistering and re-registering, you need to use io_uring_register_buffers_update_tag() (Linux 6.0+) or other newer mechanisms; otherwise, the current mechanism only supports re-registering the entire set of buffers.”