Save traces for large event/callback contexts separately

[antross]

Currently these events cannot be effectively compared if they occur in a slightly different order across traces (they just turn into big blocks of red).

Breaking them out into function calls and moving them either to a sorted order at the bottom of the trace or a separate file should help.

This way the out-of-order execution is still preserved, but turns into a single-line diff while the content of the handler block can now be independently compared.