Adding RDMA proxy for /dev/uverbsX devices to gVisor

[TheCoolDinosuar]

Based on #13297, this PR adds the --rdmaproxy flag which allows for RDMA commands to work inside gVisor sandboxes through a mostly blind passthrough proxy. This allows for ibv_devinfo, ibv_devices, ibv_rc_pingpong, and ib_write_bw to work on containers with RDMA devices mounted. It takes a lot from tpuproxy's implementation for rdmaDevice and rdmaFD to allow access to /dev/uverbsX devices. For device discovery in RDMA, it implements a new netlink protocol. Next, MR registration is also implemented in the sentry to make page pinning work. For iRDMA, reimplementing CQ/QPs is actually not necessary to get ibv_rc_pingpong and ib_write_bw to work due to CQ/QP buffers being registered as MRs. But this will need to be done for other providers.

Implements the legacy write API.
Assisted by Claude.

[ayushr2]

@TheCoolDinosuar I'm already doing this work. I will send my patches upstream shortly.