[Meta] Stable Release

Problem/Motivation

This is the meta issue to get Gin to a first stable release.

Remaining tasks

1. ✨ Move Action buttons to sticky header Needs review
2. 🐛 Table header overflow issue for multiple user role on permissions page. Fixed
3. 📌 RTL (right-to-left): change to logical CSS Needs review

After these two big initiatives are moved in and we have a new release with them, we will have to wait a while to plan in some bugfixing time. Afterwards we'll ship a first stable release and move on to use #3123907: Switch to semantic versioning 4.0.x → so we can do incremental releases afterwards.

The plan is that the first stable release will be Gin 4.0 and the 3.x branch will end with a final 8.x-3.0 release with a fade out phase with bugfixes only.

User interface changes

Form actions will always be in the sticky bar.

API changes

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Data model changes

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