Multithreading script to manually delete all the items from _totals
DynamoDB tables of the Source of Streams.

_Requirements:_
* boto3, pynamodb, source-of-streams-dynamodb-models (from The Orchard pypi)
* AWS creds in the env

_Approx. execution time for one day:_
* vendor_totals – 2 min (for ~16-18K items)
* track_totals – 50 mins (for ~3 mln items)

**PLEASE ADJUST THROUGHPUT MANUALLY BEFORE AND AFTER! But be careful: we can decrease throughput no more than 4 times per day!** 
Recommended values:
* {env}_streams_vendor_totals: RCU – 5000, WCU – 1000.
* {env}_streams_track_totals: RCU – 15000, WCU – 2000.