WiredTiger sets a limit on how much dirty content is allowed in cache based on a percentage of the total cache size. That works well for reasonably large caches, but does not scale down well.

We should either restrict how small that value can be or configure a threshold at which the dirty cache configurations are considered.

This will also be relevant for the new eviction configuration options related to the volume of updates allowed in cache that are being introduced in WT-6175.