Retry same queue (#757)

- follow up to #743
- page retries are simply added back to the same queue with `retry`
param incremented and a higher scope, after extraHops, to ensure retries
are added at the end.
- score calculation is: `score = depth + (extraHops * MAX_DEPTH) +
(retry * MAX_DEPTH * 2)`, this ensures that retries have lower priority
than extraHops, and additional retries even lower priority (higher
score).
- warning is logged when a retry happens, error only when all retries
are exhausted.
- back to one failure list, urls added there only when all retries are
exhausted.
- rename --numRetries -> --maxRetries / --retries for clarity
- state load: allow retrying previously failed URLs if --maxRetries is
higher then on previous run.
- ensure working with --failOnFailedStatus, if provided, invalid status
codes (>= 400) are retried along with page load failures
- fixes #132

---------

Co-authored-by: Tessa Walsh <tessa@bitarchivist.net>

docs/docs/user-guide/cli-options.md

@@ -240,8 +240,9 @@ Options:
                                             s         [boolean] [default: false]
       --writePagesToRedis                   If set, write page objects to redis
                                                       [boolean] [default: false]
-      --numRetries                          If set, number of times to retry a p
-                                            age that failed to load
+      --maxPageRetries, --retries           If set, number of times to retry a p
+                                            age that failed to load before page
+                                            is considered to have failed
                                                            [number] [default: 1]
       --failOnFailedSeed                    If set, crawler will fail with exit
                                             code 1 if any seed fails. When combi