When generating explain for SBE, we output two big strings:

slots - values of all slots that are set at the start of execution

stages - a detailed SBE plan

https://github.com/mongodb/mongo/blob/0a68308f0d39a928ed551f285ba72ca560c38576/src/mongo/db/query/plan_explainer_sbe.h#L88

Currently they are just added as strings to a BSONObj.

However, we have seen evidence of some plans having more than 1 000 000 slots, which means just listing slots in format `s123456 = X` may take up megabytes, even with existing truncation of strings and containers.

We should improve this code to respect internalQueryExplainSizeThresholdBytes

Otherwise we can crash not only explain, but also mask errors in regular queries (see SERVER-98493)