[Bug] Experiment results query hangs for postgres 12+

[overborn]

Summary

After upgrading our RDS from version 11 to 15, we have noticed that growthbook experiment queries, which previously took about minute to complete, currently hang for 24+ hours (with no success), keeping a 100% load of the database for Postgres 12+.
The reason is that postgres reapproched common table expressions.
In order for generated query to be able to run in reasonable time, we should be able to extend expressions like
WITH __rawExperiment as ( ... with WITH __rawExperiment as MATERIALIZED ( ...

Expected Behavior

Experiment result query should run in reasonable time (2 min or less)- same time for postres 11 and 12+

Current Behavior

Experiment result query hangs for days and loads 100% CPU for postgres 12+.