bug#59935: 29.0.60; project-list-buffers is slow

[Juri Linkov]

>> Why not leave alone that additional PREDICATE argument of
>> list-buffers-noselect, and add a feature where the BUFFER-LIST
>> argument could be a function?  That's be a compatible change.  Just
>> keep the PREDICATE argument and the code which supports it, and
>> document that if PREDICATE is a function, BUFFER-LIST cannot be a
>> function.
>
> Note the last sentence.  Doesn't it resolve the difficulty in a
> reasonable way?

Then support for a function in BUFFER-LIST should be implemented
in emacs-29?  (while keeping the recently added PREDICATE argument)