Tracing integration for [forrust_fire_tree].
The main focus of this crate is [ForestFireSubscriber], which is able to build a tree of tracing
events & spans. Since it is based on [ForestFire] which allows inserting nodes into any part
of the tree, ForestFireSubscriber is capable of tracing multithreaded applications (note that
the state is behind a mutex, so some locking will be required!).
ForestFireSubscriber is generic over the data it collects from tracing events; the event
creation mechanism is specified by your [EventProvider] implementation, or you can simply
use the built-in LogEventProvider which will collect most of the data you'd likely want
from tracing (save for timing information).
This crate is part of the forrust_fire collection.