bug#81567: 31.0.90; overlay freeze

Hello,

I found an issue related to overlays that causes Emacs to hang when
scrolling up:

The minimal reproducer I could get:
- two line overlays with empty 'display
- an overlay with 'before-string & 'display with multiple lines

When you scroll up to the beginning of the buffer, Emacs hangs. C-g does
nothing, neither does kill -SIGUSR2.

Attached is a minimal reproducer:

1. emacs -Q -l overlay-scroll-freeze.el -f overlay-scroll-freeze
2. hold C-p to move point to the start of the buffer
3. Emacs hangs when reaching the beginning of the buffer

I am pretty sure that the issue started on emacs31; although I didn't
reinstall emacs30 to verify the reproducer.