API: Remove deprecated methods

API: Remove deprecated methods

All deprecated ApiResult methods are removed. These have been deprecated
since 1.24 or 1.25, and the only users remaining in Gerrit are wrapped
in backwards-compatibility checks and so should not be being called.

ApiBase, ApiFormatBase, ApiMain, and ApiQuery methods for generating the
pre-Ib14c00df help text are removed. Nothing has called these for a long
time, and only Flow implemented them in any way. Deprecated methods for
providing the text for such help, such as getDescription(), haven't been
removed yet, though, since some extensions still call some of them.

Change-Id: I3ca7c98174b4a3f6f67f2b023e0f4446637e7a84