&phoeenniixx [BUG] change progress bar default to simple and decouple rich core dependency to avoid default failure

[fkiraly]

changes progress bar default to simple and remove rich core dependency in the model progress bar.

Fixes #600, acting on the suspicion of @phoeenniixx that the rich based progress bar is the culprit.

No deprecation is needed for the change in default, since progress bars are purely visual, and the rich based one is replaced by on-board python stdout.

[phoeenniixx]

This is working! But I was thinking we should not completely remove rich from progess_bar? We could "supress" it and add it to soft-dep for people who are already using it?

[fkiraly]

This is working! But I was thinking we should not completely remove rich from progess_bar? We could "supress" it and add it to soft-dep for people who are already using it?

I was also thinking that, but I think the problem is that there must be some version from which compatibility with lightning or similar breaks completely. So, if we leave the default as-is, then users of the default will experience, at some point, a full break of the package.

The same is true for users who explicitly set "rich" as the progress bar backend.

Hence I think - at least until we understand why rich is breaking - it is better to replace it silently. Better that the progress bar visuals change than the entire code breaking for an unclear reason, no?

[fkiraly]

We can open an issue though to track this, see #605