Implement backend top table (self, total)

#### Is your feature request related to a problem? Please describe.

The UI currently derives the functions TOP table from the flame graph. As a result of truncation happening on the flame graph data (through maxNodes), the "self" top table might be containing significant parts of "other" resource usage.

#### Describe the solution you'd like

We should calculate the top k list on the backend for each self and total and return the TOP k elements separately to the flamegraph's data.

#### Alternatives

- Just don't display others in the top table.
- Detail what self usages others has, but don't keep the tree structure.

#### Additional context

I am still a bit unsure about, how tricky the mismatches between numbers on the table and the flamegraph are for users to comprehend. Also