FIFO improvements

[chhwang]

• Revert MSCCLPP_FIFO_USE_TAIL_REPLICA=1 back to the default.
• Optimize FifoDeviceHandle.
• Do not use cudaHostAllocWriteCombined that increases latency.
• Pin host memory for Host2DeviceSemaphore::outboundSemaphore_.
• Fix proxy NUMA binding issues.
• Prevent graph capture inside proxy threads.
• Now CudaIpcConnection skips stream sync when unnecessary.
• Now any type of connection needs to hold a shared pointer to the context for memory safety.
• Now a context should be always managed by a shared pointer for memory safety.
• Minor docs & interface improvements.
• Minor fix in mscclpp-test correctness test.

[chhwang]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[chhwang]

/azp run mscclpp-test

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[Binyang2014]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).