Add capability to `PairInterface` to modify naming at time of `addSubInterface`

[mkorbel1]

Motivation

The option to expose modify is up to the constructor of an interface extending PairInterface, but at the time of adding a sub-interface is likely a point where people may want to uniquify them (e.g. multiple instances of a sub-interface).

Desired solution

Add some sort of uniqify or modify in PairInterface.addSubInterface.

Alternatives considered

No response

Additional details

No response

[mkorbel1]

Along with this, there's currently a modify in PairInterface that is not final, meaning people can change it later. This is convenient, but also "dangerous". A solution to this issue should also consider what to do about the current state of that modify function (including that people may be assigning to it, since this feature is not available yet).