Implement blueprint with onyx

[BoppLi]

Feature 645153: Create intermediate release for Vue Blueprint v3 including Onyx

• [ ] Docs for old blueprint v2 should still be deployed on a subdomain
• [ ] Replace Core UI with onyx
• [ ] Document how Core UI and onyx can be used at the same time
• [ ] Mention old version in documentation -> How to use the old v2 cli
• [ ] Deployment: Create new v3 branch migrating the blueprint to onyx -> Once v2 is officially deprecated we can merge v3 into main and it becomes the new default. (Protect v3 branch so not any inner source user can commit to it)

[mj-hof]

All the efforts for that tickets need to be booked on the blueprint solution. If you have questions, please contact me :)