As a user, advisory collection names are unique within an advisory
As a part of #4295, two advisories can be merged into a new one which contains combined package list.
Each package list consists of collections (usually 1 , but can be 0 or 2+ as well). Each collection has a name which is expected to be unique by dnf/yum client. If the name is not unique, only a subset of packages will be updated when advisory is applied on a user system.
Ensure the uniqueness of collection names at the time of combining two advisories into one.
If names are unique, preserve original names.
If names are the same, make them unique (e.g. append an ordinal number to the existing name)