Load gap packages from artifacts

[lgoettgens]

This adresses oscar-system#5345 (comment) in the way how we handle installation of deposited GAP packages inside of GAP.jl.

Additionally, this addresses a part of the issues mentioned in the CI logs of oscar-system#5345, namely (https://github.com/oscar-system/Oscar.jl/actions/runs/19213809957/job/54920128504?pr=5345#step:10:340)

      From worker 4:	#I  Package already installed at target location
      From worker 4:	#I  Target directory /home/oscarci-tester/ssd-data/ssd-runner-04/julia/scratchspaces/c863536a-3901-11e9-33e7-d5cd0df7b904/gap_packagedir_v4.15/pkg/Origami-2.0.1 exists and is non-empty
      From worker 4:	#I  Appending '.old' to old version directory
      From worker 4:	#I  Possible error detected, see log:
      From worker 4:	#I    /usr/bin/mv: cannot move '/home/oscarci-tester/ssd-data/ssd-runner-04/julia/scratchspaces/c863536a-3901-11e9-33e7-d5cd0df7b904/gap_packagedir_v4.15/pkg/Origami-2.0.1' to '/home/oscarci-tester/ssd-data/ssd-runner-04/julia/scratchspaces/c863536a-3901-11e9-33e7-d5cd0df7b904/gap_packagedir_v4.15/pkg/Origami-2.0.1.old/Origami-2.0.1': Directory not empty
      From worker 4:	#I  Could not rename old package directory

Note: there are more issues mentioned in this log, I commented about them at oscar-system#5345 (review).

@Sebas777-gif please wait with merging this until @fingolfin and/or @ThomasBreuer had a chance to look at this.

[ThomasBreuer]

Why can't we call GAP.Globals.ExtendPackageDirectories already in an __init__ function here?
For that, we need just GAP.jl, not Oscar.jl.

(Conversely, GAP.Packages.load("Origami") could then be called in src/Oscar.jl where also the other GAP packages get loaded. This would happen in particular before the __GAP_info_messages_off() call which then affects also an InfoClass that is perhaps introduced in the Origami package.)

[lgoettgens]

Indeed, this is a lot cleaner with your suggested change. I think this was just not possible with some intermediate version I was tinkering with, and I forgot to check again in the end.