Re-evaluate --bind each time bindkey pressed

[tmpm697]

Checklist

• [X] I have read through the manual page (man fzf)
• [X] I have searched through the existing issues
• [X] For bug reports, I have checked if the bug is reproducible in the latest version of fzf

Output of fzf --version

0.53.0

OS

• [ ] Linux
• [X] macOS
• [ ] Windows
• [ ] Etc.

Shell

• [X] bash
• [X] zsh
• [ ] fish

Problem / Steps to reproduce

take below example:

export test=true
fd --type file |
  fzf --bind 'ctrl-t:transform:[[ $test ]] &&
              echo "execute(echo hehe >./hehe; export test=false)+transform-query(echo $test)" ||
              echo "execute(echo kaka >./hehe; export test=true)+transform-query(echo $test)"'

press ctrl-t will always change query to true, but expect true or false between each press.

here the whole text after --bind and in single quote evaluate only one time so $test always true and somehow export test=false didn't work

expect something we can dynamically update query with fzf each time press keys, not just one.

[junegunn]

See #2976 #2299

Also related: https://github.com/junegunn/fzf/pull/3593/files