Choices for clearing/retaining trace buffer contents at Start.
A brief summary of buffer contents:
The trace buffer is divided into two main pieces: durable and non-durable.
The durable portion contains things like the string and thread data for
their respective references (trace_encoded_string_ref_t and
trace_encoded_thread_ref_t). The non-durable portion contains the rest of
the trace data like events); this is the portion that, for example, is
discarded in circular buffering mode when the (non-durable) buffer fills.