(report_overlay_modification): Fix bug#65929

(report_overlay_modification): Fix bug#65929

Somehow the new overlay code in Emacs-29 changed slightly
the test to decide when to run the `modification-hooks` of overlays,
with the consequence that these hook functions end up being executed
also when text is deleted right after an empty overlay, which is
contrary to Emacs-28 behavior as well as contrary to the Texinfo doc.

* src/buffer.c (report_overlay_modification): Better reproduce the
Emacs-28 code.

* test/src/buffer-tests.el (overlay-modification-hooks):
Add corresponding test.