Require bridges to implement `MOI.get` for `ConstraintFunction` and `ConstraintSet`

[blegat]

Currently, a bridge optimizer uses it's own cache but it serves only two purposes:

1. Implement getters for ConstraintFunction and ConstraintSet
2. Implement constraint names for bridge constraints

We should get rid of the bridge optimizer cache by:

1. Requiring bridges to implement MOI.get for ConstraintFunction and ConstraintSet
2. Implement constraint names in the bridge optimizer without relying on an MOIU.Model (similar to UniversalFallback)