Add filter/keep by http status to RecordLoader class

[greebie]

Is your feature request related to a problem? Please describe.

Now that we have http status as part of the ArchiveRecord class, it may make sense to include methods to filter and or keep record with particular status codes.

Describe the solution you'd like
Something like:

RecordLoader.loadArchives(path, sc)
  .keepValidPages()
  .filterHttpStatus(Set('404', '410'))

and same for .keepHttpStatus

Describe alternatives you've considered
@edsu also suggested that users may already expect certain Http Statuses (e.g. 410) to be removed from .keepValidPages() as well.

Additional context

See discussion in ArchivesUnleashed Slack Aut Channel.