Align v12.6 module major versions with the release version and set to 12

Since v13 we use the same version for all modules part of the release. For version 12 the minor and patch version are all aligned but not the major version, so release 12.6.11 could have modules with 5.6.11 or 6.6.11.

Since semantic versioning rules are applied for the release, the significance of the major release number is given by the product, not the individual modules.

This also hinders issue tracking and release management

To align the versions with our release, update all versions to match the release, for example

5.6.11 -> 12.6.11

6.6.11 -> 12.6.11