SCT_Monitoring: Fix undefined behavior sanitizer warning. (ATLASRECTS-5429)
ubsan warns about SCTHitsNoiseMonAlg because the class is too large. Move the large members into a separate class, an instance of which we hold via unique_ptr.
ubsan warns about SCTHitsNoiseMonAlg because the class is too large. Move the large members into a separate class, an instance of which we hold via unique_ptr.