Merge remote-tracking branch 'origin/feature/7229_muon_plotbylog_deadtime'
Re #8108. Add a test that the instrument is read in correctly.

This is for a nexus file that contains the full instrument XML.
Right now, it's still reading the external IDF - this test will make
sure things still work after the refactoring.
Merge branch 'feature/8108_load_inst_from_adara_nexus_files' into develop