[TASK] runTests.sh: composer test distribution

We're delivering a "test distribution" composer.json
in Build/composer since #94996.

The patch adds "runTests.sh -s composerTestDistribution"
that "composer update" this project and adds it to
pre-merge and nightly integrity suite.

This verifies core dependencies are fine at all times.
Main difference to the monorepo: This composer setup
has no dev dependencies that influence version decisions.

Resolves: #95188
Related: #94996
Releases: master
Change-Id: I04084a2a44a69903d523b5c4740d62d7dc46c1f1
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/71030


Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>