Tracker for state of CUDA managed/async memory support

[pentschev]

This is a meta issue to track the state of CUDA managed and async memory support.

• Add cudaMallocAsync support: done in UCM/CUDA: Add support for CUDA virtual memory with cudaMallocAsync openucx/ucx#8623, available starting from UCX 1.14+)
• Enable CUDA IPC/IB support via UCX staging buffers (UCX_RNDV_SCHEME=auto UCX_RNDV_FRAG_MEM_TYPE=cuda): done in Add RMM managed memory argument to benchmarks #836
• Enable CUDA IPC support in UCX without requiring staging buffers: will require UCX protov2
• Enable IB support in UCX without requiring staging buffers: not supportes by CUDA yet
• Fix crashes with non-IB systems when using UCX_RNDV_FRAG_MEM_TYPE=cuda: blocked by UCP_REQUEST_FLAG_RNDV_FRAG assertion failure with endpoint error handling openucx/ucx#8639, will land with UCX protov2 (default in UCX 1.16)
• Fix crash with CUDA managed memory (only seems to occur if memory is evicted): blocked by Assertion `req->send.ep == ucp_ep' failed when endpoint/process terminates openucx/ucx#8669