Compaction picker that splits input files into disjoint time windows and merges the
segments within each window. Outputs may be split further by the configured file size
threshold, at series boundaries for regions with a primary key.
Assigns files to time windows. If file does not contain a time range in metadata, it will be
assigned to a special bucket i64::MAX (normally no timestamp can be aligned to this bucket)
so that all files without timestamp can be compacted together.