UI improvements for very large traces

[esnible]

The following trace is difficult to comprehend in the Jaeger UI raw_trace_json_2.json.zip

To reproduce, unzip the file and use the JSONfile option in the UI to open it.

The trace has a large number of spans. The first operation name is /graphql so I suspect a graphql server was auto-instrumented, but the graphql library was not.

Some facts about this trace:

Total Spans: 4642 Total leaf spans: 2132 Max spans to leaf (including leaf): 21 Min spans to leaf (including leaf): 2 Average spans to leaf (including leaf): 17.3

The UI correctly renders the span. The "Trace Graph" view looks nice.

The Timeline was difficult to navigate. I could see a bit of purple async spans at the end. To zoom in on them I ended up doing

1. Select those spans with the mouse
2. ⌘ to show key bindings
3. “F” to scroll to next visible span
4. Drag the splitter so there is something on the left pane

We thought about removing some spans. One possibility is removing spans whose parent and children are on the same host. Another possibility is removing non-leaf spans that dominate. Fully one third of the spans are the operations "sssi.sscl" and "uuuwwwi.total".