[Chapel Merge] Document the `IOSkipBufferingForLargeOps` flag

Branch: refs/heads/main
Revision: 9c089fe5afddd464b48463fe8b20f41386ca6112
Author: jeremiah-corrado
Link: Document the `IOSkipBufferingForLargeOps` flag by jeremiah-corrado · Pull Request #23981 · chapel-lang/chapel · GitHub
Log Message:
Document the IOSkipBufferingForLargeOps flag (#23981)

Make the IOSkipBufferingForLargeOps flag publicly documented (and
unstable).

  • paratest
  • inspected docs

[ reviewed by @jabraham17 ] - thanks!

Compare: Comparing 179d03a1922290172860dda3a422f2877707c812...16bed66da129189c2bd74d1bf2766b618a792284 · chapel-lang/chapel · GitHub

Diff:
M modules/standard/IO.chpl
M test/io/corrado/buffering_optimization/optimization_flag.compopts
M test/io/corrado/buffering_optimization/optimization_flag.opt-off.good
https://github.com/chapel-lang/chapel/pull/23981.diff