## Problem
`l0_flush_delay_threshold` has already been set to 30 in production for
a couple of weeks. Let's harmonize the default.
## Summary of changes
Update `DEFAULT_L0_FLUSH_DELAY_FACTOR` to 3 such that the default
`l0_flush_delay_threshold` is `3 * compaction_threshold`.
This differs from the production setting, which is hardcoded to 30 (with
`compaction_threshold` at 10), and is more appropriate for any tenants
that have custom `compaction_threshold` overrides.
8afae9d03c