Re #9541. Precursor: Fix indentation issues.
Re #9541. Add a monitor workspace member to MatrixWorkspace.

Along with simple getter, setter and test.
Re #9541. Add a test of the factory behaviour.

The workspace factory should not propagate monitor workspaces.
Re #9541. Add ExtractMonitorWorkspace algorithm and test.
Re #9541. Correct doxygen omission.
Merge remote-tracking branch 'origin/feature/9541_matrixws_monitorws_member'