What are these "Version upgrade" plugins?

[Rejutka 4]

Apart from the obvious, I mean. Are they part of any normal Cura installation, or are they relicts of upgrades because I had a previous version installed? (I honestly can't remember if I had version 2.1 installed or not. The upgrade 2.1. to 2.2 is there, though. )
The progression isn't without gaps, so it could be either way...

[Smithy 1,145]

As far as I know they come with every new version to convert your existing configurations to the new version. Then they just sit in the plugins folder without disturbing or doing anything.

[ahoeben 1,981]

They are also used when loading older projects (3mf files)