Unit tests timing out on macOS

[thomashampson]

Describe the outcome that is desired.
An assortment of unit tests are hitting the 20 minute time limit on all three attempts in the nightly pipelines on the osx64 and osx-arm64 build and test stages. Some examples include:

• DirectILLAutoProcessTest (at least three runs)
• SANSILLReductionTest
• AlgorithmsTest_Q1DWeightedTest
• PowderILLDetectorScanTest
  There are probably many others that are timing out once, and then passing on the subsequent attempt.

Describe any solutions you are considering

• Decrease number of simultaneous unit tests running on macOS
• Rewrite the offending unit tests to streamline them (20 minutes for a unit test is silly)
• Move long unit tests to system tests (some of them do probably belong there)

Additional context
Why are the tests not timing out in pull request jobs?

[github-actions]

Closed by #39481.