Rewrite parts of the two ELF guides to use scripts included in the
export archive and modernize some deprecated tools and Bash idioms.
Also add the new sphinx_collapse extension to the docs build config.
Signed-off-by: Niccolò Maggioni <nicco.maggioni+nuttx@gmail.com>
Add a migration warning to the update release system and the elf
programs documentation pages. This is just to add a papertrail from
where the documentation originate in case of error during the migration
process. Also fix a bit of formatting in the pages
