Avoid interactions between the navigation and the tree

Closes #583 (closed)

• Remove the 'elementsv2/addChildren' from the navigation store
• Improve this solution with no link between the tree and the navigation https://gitlab.com/arkindex/frontend/-/commit/7d4f60c7a73c3288e9b3a6db39a9e0cd91673e9b#
• Do not store navigation elements in elementsv2 store