Re #7392. Tests for binary algorithm operator overloads

...where one of the arguments is a number.
Re #7392. Test for WorkspaceHelpers::commonBoundaries.
Re #7392. Test for WorkspaceHelpers::matchingBins.
Re #7392. Test for WorkspaceHelpers::sharedXData.
Re #7392. Test for WorkspaceHelpers::makeDistribution.
Merge remote-tracking branch 'origin/feature/7392_workspacehelpers_unit_tests'