[Investigation] Host behavior when there are matching startup type names in separate assemblies

From IcM ticket 430853269 - we need to investigate what happens when there are 2 exactly matching Startup type names from 2 separate assemblies.

In one customer's case, it seems like the "wrong" startup code was executed resulting in missing services.

No files, tests, or entry points are named. Start by reproducing the case with two exactly matching Startup type names in separate assemblies, then trace which startup code the host selects. Done means the observed selection and resulting service behavior are established and recorded.

Written by the indexing model from the issue text.