bug#46304: 28.0.50; rst-mode fill-paragraph broken in bullet-lists

[Thomas Hisch]

The indentation in a text block in a bullet-point entry is removed if it
the 2nd lines starts with a RST directive, e.g. :math:. If you run
`fill-paragraph` when `point` is somewhere on the first paragraph, the
indentation before the 2nd line is lost. This is neither the case for
the 2nd nor the 3rd bullet-point entry in this next example

* asdfasf dafd sfkdkfaslfksdflk mdfa sdfsdf kldf a kdasfd asf
  :math:`\kappa` dfaskdflsdf dasfdfas df.

* asdfasf dafd sfkdkfaslfksdflk mdfa sdfsdf kldf a kdasfd asf kksadfo
  mmommmmmasd :math:`\kappa` dfaskdflsdf dasfdfas df.

* asdfasf dafd sfkdkfaslfksdflk mdfa sdfsdf kldf a kdasfd asf asdfasf
  dafd sfkdkfaslfksdflk mdfa sdfsdf kldf a kdasfd asf asdfasf dafd
  sfkdkfaslfksdflk mdfa sdfsdf kldf a kdasfd asf asdfasf dafd
  sfkdkfaslfksdflk mdfa sdfsdf kldf a kdasfd asf dakkkkkkkkkkkkkkkk
  :math:`\kappa` dfaskdflsdf dasfdfas df.


In GNU Emacs 28.0.50 (build 1, x86_64-pc-linux-gnu, X toolkit, cairo version 
1.16.0, Xaw3d scroll bars)
 of 2021-02-03 built on NBPF1PQX4B
Repository revision: b81516c7fb558c9b4bc44e6e69f6729a5f2f9894
Repository branch: master
Windowing system distributor 'Fedora Project', version 11.0.12010000
System Description: Fedora 33 (Workstation Edition)

Configured using:
 'configure 'CFLAGS=-march=native -O3' --prefix=/opt/emacs
 --with-x-toolkit=lucid --with-xpm --without-jpeg --without-gif
 --without-tiff --with-modules --with-json'

Configured features:
ACL CAIRO DBUS FREETYPE GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JSON
LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES NOTIFY INOTIFY
PDUMPER PNG RSVG SOUND THREADS TOOLKIT_SCROLL_BARS X11 XAW3D XDBE XIM
XPM LUCID ZLIB

Important settings:
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: ReST

Minor modes in effect:
  counsel-projectile-mode: t
  counsel-mode: t
  ivy-rich-mode: t
  ivy-mode: t
  global-ethan-wspace-mode: t
  save-place-mode: t
  show-paren-mode: t
  delete-selection-mode: t
  savehist-mode: t
  global-hi-lock-mode: t
  hi-lock-mode: t
  winner-mode: t
  window-numbering-mode: t
  global-undo-tree-mode: t
  undo-tree-mode: t
  thi::spell-fu-mode: t
  spell-fu-mode: t
  async-bytecomp-package-mode: t
  recentf-mode: t
  global-git-commit-mode: t
  magit-auto-revert-mode: t
  global-flycheck-mode: t
  flycheck-mode: t
  flx-ido-mode: t
  shell-dirtrack-mode: t
  evil-mode: t
  evil-local-mode: t
  projectile-mode: t
  override-global-mode: t
  url-handler-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  global-prettify-symbols-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  size-indication-mode: t
  column-number-mode: t
  line-number-mode: t
  auto-fill-function: yas--auto-fill
  transient-mark-mode: t

Load-path shadows:
/home/thomas.hisch/.emacs.d/elpa/magit-20210203.1158/magit-section hides 
/home/thomas.hisch/.emacs.d/elpa/magit-section-20210124.1824/magit-section
/home/thomas.hisch/.emacs.d/user-lisp/custom hides 
/opt/emacs/share/emacs/28.0.50/lisp/custom

Features:
(shadow sort mail-extr emacsbug sendmail reporter shortdoc rst
git-rebase pcmpl-unix mc-hide-unmatched-lines-mode mc-mark-more ...)

Memory information:
((conses 16 1369556 1178269)
 (symbols 48 92372 85)
 (strings 32 433122 105720)
 (string-bytes 1 12547904)
 (vectors 16 139013)
 (vector-slots 8 3290135 820691)
 (floats 8 1055 1564)
 (intervals 56 75226 43134)
 (buffers 984 119))
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