Remove infinity QuantityDicts from PDController, and replace usage

[balacij]

Contributes to #2892

Definite integration with infinite bounds becomes indefinite integration, which is why 'stable' changes slightly.

[JacquesCarette]

Except that seems wrong? We really do want this to display in the 'usual' way.

[JacquesCarette]

Removing the infinity symbols from PDController is good (they should be in drasil-data!).

However, there should also be a display rule where if the integral is a definite integral on the whole domain, then it should display using infinite bounds. This is different than an indefinite integral!

[balacij]

Would we want infinity to be represented by a QuantityDict? Do you think it would be better to represent infinity in ModelExpr instead?

Ah, I've forgotten my improper integrals; I felt that something might've been wrong, but I couldn't quite tell what. Thank you! I will revert that change.

[JacquesCarette]

We'd want infinity to be represented in the same way pi is. We don't want to embed either of them too deeply into Drasil. Take a look at Range for how I side-stepped having to 'write down' infinity in expressions, but how infinity can still appear in output if we so wish, because it is semantically present in the representation (even if it is not syntactically there).

[balacij]

Since this PR is stale and I think what @JacquesCarette would require us to rewrite this PR anyways, I'll go ahead and close this PR.