* Refactor `collect_uncleaned_pubkeys_to_slot()`
While working on another issue (#16580), I came across
`collect_unclean_pubkeys_to_slot()` and had difficulty understanding it.
Since the function does a few logically separate things, I split the
function up. I also added documentation, removed an unused return value,
and renamed the functions to be more specific.
This commit is to split up an existing PR (#16786), where I had both this
aesthetic change _and_ a behavioral change.
1eaff394da