[metrics-bugs] #26190 [Metrics/Statistics]: Use slf4j throughout all stats modules

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#26190: Use slf4j throughout all stats modules
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     Reporter:  iwakeh              |      Owner:  metrics-team
         Type:  enhancement         |     Status:  new
     Priority:  Medium              |  Milestone:
    Component:  Metrics/Statistics  |    Version:
     Severity:  Normal              |   Keywords:
Actual Points:                      |  Parent ID:
       Points:                      |   Reviewer:
      Sponsor:                      |
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 Some modules, for example ipv6servers, use slf4j for logging, others, bad
 example hidserv, use System.err/out for logging.

 Check all org.torproject.metrics.stats sub-packages and make them use
 slf4j.
 Secondly, create an appropriate logback.xml file and adapt the run-java
 ant-task to use logback logging.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/26190>
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