Add readgroup level stats config option for Picard metrics

[EddieLF]

Adds a config option for the Picard CollectMultipleMetrics job, to allow alignment summary metrics to be collected at a read group level, as opposed to at a sample level where all read groups are squished together.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.62%. Comparing base (8ad2ba3) to head (de4486b).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #910   +/-   ##
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  Coverage   78.62%   78.62%           
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  Files          10       10           
  Lines        1792     1792           
=======================================
  Hits         1409     1409           
  Misses        383      383           

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