Richer, non hierarchical topology filters in graph view

**Is your feature request related to a problem? Please describe.**
The multi cloud view currently always starts at the root (cloud providers), and then allows you to drill down expanding nodes. The view supports filters, but filters are hierarchical too: you can filter on a cloud provider, then its children, then grandchildren etc.

It would be useful to be able to express more advanced filters, eg "show all kubernetes clusters and fargate tasks", and then be able to drill down as usual.

**Describe the solution you'd like**
We should replace the current filters with more expressive, non hierarchical filters. The multi cloud view should show the applied filters as the root nodes (as opposed as always showing cloud providers as root nodes). The filters should be *bookmarkable* (somehow persisted in the URL), so that users can save and switch between alternate topology views easily, and the UI can provide inter linking between views.

**Components/Services**

- [x] UI/Frontend
- [x] API/Backend
- [ ] Agent
- [ ] Deployment/YAMLs
- [ ] CI/CD Integration
- [ ] Other (specify)