It shadows the unicode function of the same name, and there's no
way to entirely disambiguate the two based on the parameter passed
in. This change deprecates Message.translate and makes it a wrapper
around the new function, Message.translation.
Note that we never documented calling Message.translate directly.
The documented way to get the translated form of a Message is to call
the _translate.translate function in this project, so chances are
that this public API change will have little actual impact on users.
Change-Id: I0c617937f5af7467d1454f72acd0474ae2ce0293
Closes-Bug: 1841796