Fix/make role and group utils pub

[maltesander]

Description

• more public v2 framework stuff adapted

Please add a description here. This will become the commit message of the merge request later.

Definition of Done Checklist

• Not all of these items are applicable to all PRs, the author should update this template to only leave the boxes in that are relevant
• Please make sure all these things are done and tick the boxes

Author

• Changes are OpenShift compatible
• CRD changes approved
• CRD documentation for all fields, following the style guide.
• Integration tests passed (for non trivial changes)
• Changes need to be "offline" compatible

Reviewer

• Code contains useful comments
• Test cases added
• Changelog updated: Can be postponed until the branch smooth-operator is merged into main
• Cargo.toml only contains references to git tags (not specific commits or branches)

Acceptance

• Feature Tracker has been updated
• Proper release label has been added

[siegfriedweber]

Which change makes the role and role group utils public?

There are build errors (on my machine):

error[E0433]: cannot find `stackable_operator` in the crate root
   --> crates/stackable-operator/src/v2/role_utils.rs:222:21
    |
222 |     #[derive(Debug, Fragment, PartialEq)]
    |                     ^^^^^^^^ could not find `stackable_operator` in the list of imported crates
    |
    = note: this error originates in the derive macro `Fragment` (in Nightly builds, run with -Z macro-backtrace for more info)
help: consider importing this module through its public re-export
    |
200 +     use crate::v2::role_utils::fragment;
    |