This will require that entries for renamed files be updated so that they don't
accidentally start being loaded under the new name later. It also prevents
dead code entries from sticking around after their targets are removed.
Using `throttledMapPromises` is probably not strictly necessary given the
small number of entries in most lists, but since it already exists, we may as
well use it here.
Differential Revision: https://phabricator.services.mozilla.com/D150921
0e66c24b37
