The "Regenerate title" session-menu action (#3223) added five i18n keys
(session_title_regenerate, _desc, _regenerating, _regenerated,
_regenerate_failed). They shipped as English text in every non-English
locale block.
Translate all five keys across it, ja, ru, es, de, zh, zh-TW, pt, ko,
fr and tr, matching each locale's existing terminology (e.g. the word
used for "title" in session_rename_desc). zh and zh-TW are written as
\u escapes to match the existing style of those blocks.
Closes#3364