[TASK] Have static DP in StreamTest

Clean up and simplify a bit along the way.

Resolves: #100396
Related: #100249
Releases: main
Change-Id: I821c2c8e19aed4f4c1636eadf328d46a3dbc8c5c
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/78370


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