[growth] Implement growthInsertionIndex for vertices

We also need to know which indices a vertex had at insertion in case we need to attach data to a vertex during growth. This was already implemented for elements, but is necessary for vertices too.

added 7 commits

• d0d59755...f9e6861e - 6 commits from branch master
• 700227cf - [growth] Implement growthInsertionIndex for vertices

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assigned to @oliver.sander

merged

mentioned in commit 3f3671c4