Korean input issue

[aca]

It seems korean input is broken in nightly.
Creating this issue in the hope that Korean users can gather, organize, and resolve related issues.

WIP

• fix: inconsistent behavior from legacy and kitty Key encoding #5728
• macos: requires two <esc> to exit insert mode in vim with korean ime. #1663

Fixed

• input: fix bs emitting sequence when it should not #1665
• input: do not emit sequence on <BS> when their's UTF-8 text #1659
• input: escape can be used to clear dead key state #1651
• apprt/gtk: commit buffer before "preeditchanged" resets #1594
• macos: handle preedit in AppKit, enables Korean input #856

cc @exploitJ @leokang94

[aca]

띄어쓰기시 글자가 지워지는 현상, linux/nixos/wayland/fcitx5

'한글<space>' // got: '한<space>', expect: '한글<space>'