[BUG] src and example blocks do not properly escape headings [9.6.6 (release_9.6.6 @ /usr/share/emacs/30.0.50/lisp/org/)]

[Vladimir Nikishkin <lockywolf@gmail.com>]

Hello, everyone,

My MWE is the following:

```
Hello, preamble.

* Heading one

body one

#+begin_src org
* heading 2
#+end_src

#+begin_example
* heading 3
#+end_example

#+begin_verbatim
* heading 4
#+end_verbatim


```

Clearly, "heading 2", "heading 3", and of course, "heading 4" should not
be considered headings of the original document. However, here they are
treated as normal headings, in particular, they are not just breaking
the folding logic, they are even breaking the detection of begin_*/end_*
blocks.

I have a feeling that this was not the case in the past...?

Emacs  : GNU Emacs 30.0.50 (build 1, x86_64-slackware-linux-gnu, GTK+ Version 3.24.31, cairo version 1.16.0)
 of 2023-07-31
Package: Org mode version 9.6.6 (release_9.6.6 @ /usr/share/emacs/30.0.50/lisp/org/)
-- 
Your sincerely,
Vladimir Nikishkin (MiEr, lockywolf)
(Laptop)