deprecate getDisplayInfo

[turadg]

What is the Problem Being Solved?

It's a UI concern, not relevant to inter-vat communication.

Description of the Design

We still need some authority that UIs can use for stuff like alleged names or decimal places. We have that in vstorage with boardAux (see #8627)

That's all UIs need. They can't call getDisplayInfo() anyway.

Security Considerations

Scaling Considerations

Test Plan

Upgrade Considerations