Revert !63549
Enabling SharedWriter by default seems to have caused a few issues in upstream workflows. Unfortunately, none of these were caught by the CI (but by ART - so it's a glass half full/empty situation). Anyways, for now, let's revert !63549 (merged) until all details are sorted out. I created ATEAM-912 to follow up on the necessary work.
Closes ATLASRECTS-7656, ATEAM-910, ATLSWUPGR-196, ATLASSIM-6598, and ATLASSIM-6601.