[DISCUSS] Should we start marking "feather" as deprecated?

[Weston Pace]

Feather V2 is currently synonymous with the IPC format.  My impression
is that the feather terminology is now being deprecated in favor of
IPC.  Do we want to start marking feather modules as deprecated (both
in code and the documentation) and more explicitly point users to the
newer RecordBatchFileReader / RecordBatchStreamReader alternatives?