Update the BUILD number to 4596.
Update the BUILD number to 4596.

* Removed the "[全]" description from fullwidth-only characters.
* Created japanese_util.cc from util.cc
* Replaced utility functions with Abseil functions.

PiperOrigin-RevId: 418122636

fcitx/mozc,google/mozc,google/mozc,google/mozc,google/mozc,fcitx/mozc,fcitx/mozc,google/mozc,fcitx/mozc,fcitx/mozc