coll: use MPI_Aint for v-collective array parameters

[hzhou]

Pull Request Description

Last PR (#5044 ) switched to use MPI_Aint for all internal collective routines. This PR does the same for the counts/displs array for v-collectives.

Also added python code to generate MPI_Aint impl prototypes and generate
code to do counts array swap before calling MPIR_Xxx

Expected Impact

Author Checklist

• Reference appropriate issues (with "Fixes" or "See" as appropriate)
• Remove xfail from the test suite when fixing a test
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• Passes all tests
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[hzhou]

test:mpich/ch3/most
test:mpich/ch4/most

[hzhou]

test:mpich/ch3/most

[raffenet]

Just to add some data here, I ran some simple experiments to measure the overhead of promoting these arrays. Using OSU benchmark for MPI_Alltoallv (4 it JLSE nodes, fully subscribed ppn=88) with actual communication in MPICH commented out (i.e. message size is irrelevant):

Original MPICH

# OSU MPI All-to-Allv Personalized Exchange Latency Test v5.4.1
# Size       Avg Latency(us)
1                       1.15

With large count promotion

# OSU MPI All-to-Allv Personalized Exchange Latency Test v5.4.1
# Size       Avg Latency(us)
1                       2.58

Actual communication cost

For reference, actually communication cost for MPI_Alltoallv (over TCP), leads me to believe this overhead may not be significant:

# OSU MPI All-to-Allv Personalized Exchange Latency Test v5.4.1
# Size       Avg Latency(us)
1                   35231.28

[raffenet]

This is definitely pushing the boundaries of what a single commit can change, but I suppose it is unavoidable given all the APIs that depend on the array arguments.

[raffenet]

Here is communication data from Gomez w/ Infiniband (ch4:ucx):

# OSU MPI All-to-Allv Personalized Exchange Latency Test v5.4.1
# Size       Avg Latency(us)
1                    2029.23

[hzhou]

test:mpich/ch4/ofi

[hzhou]

Reference #4880