Move some things out of the Main Package

[PaulJonasJost]

We might consider moving some packages out of the main package if they are not used regularly anymore but create a lot of work on fixing issues. (e.g. Aesara)

[FFroehlich]

I think aesara can simply be removed.

[dweindl]

I think aesara can simply be removed.

Fine with me.

It might be good to have some policy on removing/adding new/old interfaces with respect to versioning and to whether they should be here or in separate packages.

[PaulJonasJost]

In light of recent fails due to aesara, will remove it now and come up with policy that can be discussed.