API: Fix ApiFormatFeedWrapper

With recent changes to the API, directly outputting text from execute()
in ApiFormatBase subclasses doesn't work anymore. Adjust
ApiFormatFeedWrapper for this new situation, and also handle headers in
initPrinter() where that belongs.

Bug: 72359
Change-Id: I4e4a2386858da6d87169deabaca763eeeacefbe9
Merge "API: Fix ApiFormatFeedWrapper"