Merge() is always returning a copy, so there is no need to Copy()
struct fields first before calling Merge() on them.
This reduces GC pressure (#1010) and helps overall app performance
(#1457).
Squash of:
- including children in topologies_test.go
- report.Node.Prune should prune children also
- rewrote ShortLivedInternetConnections test to express its intent
- adding tests for detail Summary rendering
Squash of:
- use detailed.Summaries to render topology nodes
- ban merging nodes of different topologies (they should be mapped)
- need to prune parents when mapping node types
- render container images by id if they have no name
- remove separate render ids and prune parents in NewDerived*
- don't render metrics/metadata for groups of nodes
- fixing up tests
- removing pending unit tests (for mapping.go, for now)
- updating experimental dir for RenderableNode removal
