refactor(navigation): Group plugin menu items

[pheus]

Pull Request

Related Issue

Fixes: #255 [Feature] Group Navigation Items

New Behavior

• Groups navigation items under Access Lists, Rules, and Assignments for improved readability and maintainability.
• Splits menu definitions into distinct variables for better clarity.

Contrast to Current Behavior

• Previously, navigation items were listed without logical grouping.
• This refactor enhances structure but introduces no functional changes.

Discussion: Benefits and Drawbacks

• Improves navigation efficiency, making it easier to locate relevant items.
• Enhances scalability, ensuring a well-organized menu as new models are introduced.
• Primarily a cosmetic improvement, but contributes to a better user experience.

Changes to the Documentation

None required.

Proposed Release Note Entry

• Reorganized the plugin menu, grouping items under Access Lists, Rules, and Assignments.

Double Check

• I have explained my PR according to the information in the comments
  or in a linked issue.
• My PR targets the dev branch.