Better automatic Singular banner hiding

[fingolfin]

My students are writing a package which depends on Oscar. Loading their package in Julia 1.8.2 shows the Oscar banner, but also the Singular and Polymake banners. We have logic in place which is supposed to prevent this. Perhaps it needs to be update in a similar fashion to what @thofma did in oscar-system/GAP.jl#826 ?

(Perhaps we should move this logic into a helper function and put it into a helper package that is then used by GAP.jl, Singular.jl, Polymake.jl -- this way we only need to update this and a few other things in only one place? Or even without the package, if there was an identical helper function used in all three packages, updating it would be easier).

See also oscar-system/Polymake.jl#412

[fingolfin]

Resolved by PR #668