Fix bug4821 - Some tests request an incorrectly large segment size

[bonachea]

In FAST/LARGE segment modes, always validate the segment size
request we're about to pass into gex_Segment_Attach or gasnet_attach
fits within gasnet_getMaxLocalSegmentSize, otherwise issue a
user-friendly error message.

Example testvis output (from a docker container with default shm):

ERROR: node 1/4 Test requested a GASNet segment of size=16777216, but this exceeds the currently available gasnet_getMaxLocalSegmentSize()=10477568.
You may need to adjust the memory resource limits of this system/shell, otherwise adjust test parameters to reduce segment utilization requirements. (at [redacted]/gasnet/tests/test.h:1023)

[PHHargrove]

LGTM. Thanks for addressing this so quickly.

If it is not too much trouble, it might be wise to defer merge of this PR until after merge of my (soon to appear) PR to fix gex_Segment_Attach() to reject the oversized requests. Otherwise, this will eliminte the original reproducers for my issue.

[bonachea]

If it is not too much trouble, it might be wise to defer merge of this PR until after merge of my (soon to appear) PR to fix gex_Segment_Attach() to reject the oversized requests. Otherwise, this will eliminte the original reproducers for my issue.

I'm in no rush to merge.
However FWIW the testhello with a numeric argument can still be used to reproduce bug 4822, because it (deliberately) does not use these test.h wrappers, and instead passes the segment size argument directly to gex_Segment_Attach

[PHHargrove]

[...] FWIW the testhello with a numeric argument can still be used to reproduce bug 4822

Valid point. I withdraw my request to defer merging this PR.