bug#72523: 28.1; rst.el: indentation from TAB key in rst mode (ReST) is wrong when directive as an option

[Eli Zaretskii <eliz@gnu.org>]

> From: jfbu <jfbu@free.fr>
> Date: Thu, 8 Aug 2024 14:53:13 +0200
> 
> Consider editing in Emacs a file `test.rst` and having typed so far
> 
> ~~~rest
> .. note::
>    :name: test
> ~~~
> 
> then insert a blank line and hit the TAB key on next one.  The cursor will align with `test`,  not with `:name:`.
> 
> This produces extra space in output when processed either by rst2html or integrated into a Sphinx projet.  For context see [this Sphinx comment](https://github.com/sphinx-doc/sphinx/issues/12742#issuecomment-2275622334).
> 
> I am using a file rst.el.gz integrated to my Emacs 28.1 which contains
> ~~~lisp
> ;; Maintained by the release process.
> (defconst rst-official-version
>   (rst-extract-version "%" "OfficialVersion: " "[0-9]+\\(?:\\.[0-9]+\\)+" " "
> 		       "%OfficialVersion: 1.5.2 %")
>   "Official version of the package.")
> (defconst rst-official-cvs-rev
>   (rst-extract-version "[%$]" "Revision: " "[0-9]+\\(?:\\.[0-9]+\\)+" " "
> 		       "$Revision: 1.1058.2.9 $")
>   "CVS revision of this file in the official version.")
> ~~~
> 
> I tried with electric-indent-mode both on and off.  No change.

Stefan, any comments or suggestions?