R1:3b92da22f433

Move the hierarchical edit policy check in Phriction from requireCapabilities() to validateTransactions()

Summary:
Depends on D19583. Ref T13164. This continues the work of getting rid of `requireCapabilities()`.

This check is valid, but can be a `validateTransactions()` check instead. This is generally more consistent with how other applications work (e.g., creating subprojects).

The UI for this isn't terribly great: you get a policy error //after// you try to create the object. But that's how it…