Allow comparators access to the complete list of entries

[scratchyone]

This is a small change that allows comparators to access the entire list of entries, by adding an optional comparator argument that contains the current list of completion entries. This makes it easier for slow comparators (for example, something requiring an API call, disk I/O, or ML model execution) to batch their computations, execute them all at once, and then return cached results for the rest of the comparisons.