bug#40808: 27.0.91; inaccuracy in isearch-lazy-count

[Juri Linkov]

>> I'm still unsure about pushing this change.  The current state of things:
>>
>> - in emacs-27 and master now it counts all matches, including invisible,
>>   regardless of the value of search-invisible;
>>
>> - the proposed change for master doesn't include in the count these
>>   invisible matches that can't be visited by opening overlays;
>>
>> - but this fix is pointless for org-mode where visiting invisible
>>   matches is broken, and where its count varies after visiting
>>   and opening hidden overlays.
>
> Would it be possible to fix the breakage in Org on master?

We need help from Org developers to fix the breakage in Org.

Meanwhile, I reverted a part of the recent fix on emacs-27
that tried to fix a long-standing corner case of lazy-highlighting
in outlines, but whose side-effect might slow down lazy-highlighting
in collapsed outlines.  This needs more testing on master.

Whereas the fix for isearch-lazy-count still remains in the release branch.