[DAR-2045][External] Multi-threaded annotation imports

[JBWilkie]

Problem

Importing annotations only works in a single-threaded fashion. This results in a significant bottleneck when sending import API requests in series

Solution

Add optional multi-threading to significantly improve speed when importing annotations. Pass the use_multi_cpu flag as True to enable multi-threading

Changelog

Added option to import annotations with multi-threading, resulting in significant speed gains

[linear[bot]]

DAR-2045 Implement multi-threading when sending import annotation requests