Implement MMIO with put and signal

[Binyang2014]

This implementation using mmio to copy data from two devices. The process is:

GPU 1 ---->GPU 2 -----> GPU 3 ---> ... ---> GPU 8----> GPU 1

Test results for 1n-8p 1KB data, ring send-recv:

# minBytes 1024 maxBytes 1024 step: 1048576(bytes) warmup iters: 10 iters: 50 validation: 1 graph: 15, kernel num: 0
#
#
# Initializing MSCCL++
# Setting up the connection in MSCCL++
# Launching MSCCL++ proxy threads
#
#                                    in-place                       out-of-place          
#       size         count     time   algbw   busbw  #wrong     time   algbw   busbw  #wrong
#        (B)    (elements)     (us)  (GB/s)  (GB/s)            (us)  (GB/s)  (GB/s)       
        1024           256    37.81    0.22    0.19      0
Stopping MSCCL++ proxy threads
# Out of bounds values : 0 OK
#

Result for nccl using simple protocol for send-recv test

#
#                                                              out-of-place                       in-place          
#       size         count      type   redop    root     time   algbw   busbw #wrong     time   algbw   busbw #wrong
#        (B)    (elements)                               (us)  (GB/s)  (GB/s)            (us)  (GB/s)  (GB/s)       
        1024           256     float     sum      -1    20.44    0.05    0.05      0    25.15    0.04    0.04    N/A
# Out of bounds values : 0 OK
# Avg bus bandwidth    : 0.0454108 
#

Will optimize it in following PR