Re #7750. Add boilerplate code to stop constructor running every time.

In particular, the constructor for FilterPeaksTestPerformance was running
LoadIsawPeaks every time any Crystal test was run.
Re #7750. Add boilerplate code for perf. tests with constructors.

None of these other constructors did much, but there's no harm in having
this here anyway (someone might make them do something in the future).
Merge remote-tracking branch 'origin/bugfix/7750_protect_perf_test_constructors'