Ra metrics fixes and release notes #14739
                
     Merged
            
            
          
  Add this suggestion to a batch that can be applied as a single commit.
  This suggestion is invalid because no changes were made to the code.
  Suggestions cannot be applied while the pull request is closed.
  Suggestions cannot be applied while viewing a subset of changes.
  Only one suggestion per line can be applied in a batch.
  Add this suggestion to a batch that can be applied as a single commit.
  Applying suggestions on deleted lines is not supported.
  You must change the existing code in this line in order to create a valid suggestion.
  Outdated suggestions cannot be applied.
  This suggestion has been applied or marked resolved.
  Suggestions cannot be applied from pending reviews.
  Suggestions cannot be applied on multi-line comments.
  Suggestions cannot be applied while the pull request is queued to merge.
  Suggestion cannot be applied right now. Please check back later.
  
    
  
    
document Ra metrics -> Ra counters transition
while documenting the changes, I noticed some problems with which metrics are returned when,
so this PR also fixes these issues.
/metricsreturns all coordination system metrics and somehigh-level QQ values
/metrics/per-objectreturns all coordination metrics and selectedmetrics for quorum queues
/metrics/detailedall queues as well as all coordination system metrics
for all queues in that vhost, but doesn't return coordination metrics