This migrates existing code from the old TranslateKey(s) endpoints to the newer CreateKeys and FindKeys endpoints.
The CreateKeys and FindKeys endpoints were created previously as the TranslateKeys endpoint had no way to behave sanely when the looked-up key did not exist (the parallel-arrays representation did not have a good way to represent a missing key).
This change also removes the old TranslateKey(s) functions from the translation stores.
It leaves a wrapper emulating the TranslateKey(s) endpoints so that old idk still works for now.
Attributes are unmaintained and unused.
They have become more of a liability than a benefit.
This change eliminates them from the codebase.
The only user-visible change (assuming that attrs are not used) is that the attrs field will no longer appear in row JSON.
