ISW - Input Diagnosis Improvements

[grotlue]

• Received Message count by Stream: clickable link to stream
  • We need to adjust the API system/inputs/diagnostics/${inputId} to include the stream id so we can build a link
• Content for Input Diagnosis step in input setup wizard (@tellistone, we need copy for that)
• Add Active Connections metric (same like on inputs list) to the page
• Use correct metrics
• Add new metric org.graylog2.inputs.${inputId}.failures.input as the asterix notation in org.graylog2.inputs.codecs.*.${inputId}.failures does not work
• Add feature tests
• Add new metrics that represent total in last 15 minutes instead of messages per second

[grotlue]

We cannot build a link for "Message Error at Input" as we don't save them yet
@AntonEbel can you check if and how we can build links to "Message Failed to process" and "Message Failed to index" (using failure_type field?)

[grotlue]

All three metrics we use are per second metrics. I checked with @tellistone and it is preferred to not use per second metrics but rather a "total in the last 15 min" metric. Can we add new metrics for that @AntonEbel?