rP37e26f1b4531

Improve rendering of "default value changed" custom form transactions to at least have all the information

Summary:
Ref T13319. Currently, transactions about changes to a default form value use a raw internal key for the affected field and don't show the actual value change.

An ideal implementation will likely require us to specialize a great deal of rendering, but we can do much better than we currently do without too much work:

- Try to pull the actual `EditField` object for the key so we can…