SI-7479 Add avian option to partest's diff filter...

... so that the different results of the test on Avian
can be specified in the check file.
Add Duration.toCoarsest method
SI-7479 Make test/files/run/tailcalls.scala pass on Avian

This commit modifies the test and check file to use the new diff filter.
Merge pull request #2561 from soc/SI-7479

SI-7479 Make test/files/run/tailcalls.scala pass on Avian
Merge pull request #2602 from t3hnar/Duration.toCoarsest

Add Duration.toCoarsest method