Migration event hashing to new algorithm

[poulok]

Use the new hashing algorithm for new events. Hash old events according to the old algorithm. Put the new hashing algorithm for new events behind a feature flag such that it is only used for new events when the flag is enabled.

This ticket must not be completed until performance testing is complete. The performance tests do not need to "pass", but there must be results that inform the next steps of the project. The test must have high event volume, therefore it must be on a large network. Either perf1 or engnet2.