Instead of crashing when the bufbuilder size reaches some hardcoded max-size, we can make it configurable (and call it "journal cache size"), and do a stop-the-world (pause all writes to it) if the max-size is reached.

This strategy is better than what we have right now, as it allows the user to make a choice based on his concurrency requirements, in a somewhat similar fashion he can configure the cache size in WT.

In the event of reaching max-size, the user won't see his server crashing but will experience a short performance degradation, which is better in most cases.