Upgrade to Vue 3

### Current Behavior

Frontend now uses outdated Vue 2

### Proposed Behavior

Move to Vue 3 after #445 is resolved:
- upgrage to Vue 3:
- https://v3-migration.vuejs.org/
- https://www.vuemastery.com/blog/vue-3-migration-build/
- https://www.vuemastery.com/blog/migration/
- Upgrade BoostrapVue 2 -> 3 (not available yet: https://bootstrap-vue.org/vue3)
- upgrade to Bootstrap 5
- Upgrade to CoreUI 4.x
- Replace vue2-org-tree by https://www.npmjs.com/package/vue3-blocks-tree
- upgrade other dependencies

### Checklist

- [X] I have read and understand the [contributing guidelines](https://github.com/DependencyTrack/dependency-track/blob/master/CONTRIBUTING.md#filing-issues)
- [X] I have checked the [existing issues](https://github.com/DependencyTrack/frontend/issues) for whether this enhancement was already requested