[TASK] Avoid root-only fields in extensions composer.json

composer.json fields marked as root-only in
https://getcomposer.org/doc/04-schema.md are only
used if the composer.json is used as project root.

Core extensions and split repositories are never used
as project root directly and also won't work as such.
Testing is always performed on the monorepo.

All root-only fields are thus obsolete in extensions
composer.json, namely: require-dev, autoload-dev,
minimum-stability, prefer-stable, repositories,
config, scripts.

sortpackages: true in config field is kept since
this is useful when updating packages using
componer req something -d typo3/sysext/core_ext

Resolves: #94747
Releases: master
Change-Id: I9712703c35ef3d00c098bc58218032d1e19306d4
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/70288


Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>