Callstack frames will now have nullptr as the value in the callstackFrameMap
map, as a way to signal that a query for given key is already pending.
Duplicate queries should no longer happen.
@slomp provided alternative implementation, which produced the following
results:
Queries made: 195,778
Duplicate queries skipped: 9,518,910
Co-authored-by: Marcos Slomp <slomp@adobe.com>