ESQL: IAEs in the compute engine report as 400 status codes #128963
Description
An IllegalArgumentException in the compute engine is almost certainly a bug, and should result in a 500 status code. Unfortunately, our action listeners pick up IAEs and automagically turn them in to 400 responses.
We need to check all IAEs in the compute engine/in the ESQL code and make sure they don't get reported as 400 codes, or make it so all IAEs (or just all uncaught exceptions/exceptions we don't report as warnings?) in the compute engine become 500s.
Otherwise, we lose the ability to quickly notice bugs by looking at the 5xx responses processed by the proxy.