cubicweb #7446353 CWConstraintAddOp prevents two constraints of the same type on a rdef [validation pending]

While this makes sense for some constraint types (such as vocabulary or size), it's not generally applicable. And, it makes the in-memory schema inconsistent with the in-db schema (where two constraints of the same type can co-exist just fine), so the operation should really not remove existing constraints from the list.

prioritynormal
typebug
done in3.22.0
load1.000
load left0.000
closed by#ab626726a70a [syncschema] don't arbitrarily remove constraints from the in-memory schema
patch[syncschema] don't arbitrarily remove constraints from the in-memory schema [applied]