Re-enable build with snapshots for the different branches and Hibernate ORM versions

[DavideD]

I think we need the following separate branches for the different ORM version:

• Hibernate Reactive 2.3 with Hibernate ORM 6.5
• Hibernate Reactive 2.4 with Hibernate ORM 6.6
• Hibernate Reactive 3.0 with Hibernate ORM 7.0

A summary of the branches is available here: https://github.com/hibernate/hibernate-reactive/branches

I've decided to create separate branches where we can test the snapshots, and we will test non snapshots versions in main. This way, main won't fail as often and we can apply fixes when needed on the snapshots branches.