Feature request: be able to add multiple seperate triggers to programs plugin with different priority

**The motive is to make it possible to assign priorities/orderings/triggers seperately to different sources, makes found programs deduplication less annoying.**

For the current time being, programs plugin does not deduplicate found programs among different sources, also there is no ways to assign different priorities for programs found with different sources.

To meet this need, it seems that it could be done with multiple parallel programs plugin configuration, which is not a function provided yet.

For my specific use case, I have a folder C:\GreenSoft\Launcher that collects all common shortcuts sorted in different sub folders, which is indexed by programs plugin explicitly. I assign it with high priority and triggered by `*`.

But I still need to index all other default programs sources like start menu etc., this time I'd like to give them low default priority and trigger by `app` prefix explicitly.

Start by tracing the programs plugin configuration and the handling of sources, priorities, triggers, and found-program deduplication. Compare the requested parallel configurations with the existing single configuration. Done means different sources can use separate priorities and triggers, while programs from those sources are deduplicated as intended.

Written by the indexing model from the issue text.