R1:b08c9b3ffa8a

Remove extra container tag on HandleListViews rendering from ModularTransactions in text mode

Summary:
Fixes T12082. Ref T11114. When modular transaction render a handle list, they use HandleListView, which has a text mode.

However, the HandleListView is a TagView, and currently TagViews always render a tag of some kind. Allow them to return `null` to decline to render any tag.

Test Plan:
- Added a pile of debugging stuff to `ApplicationTransactionEditor` to throw during mail generation.
- Added a…