Metric interface clean up

[sushobhan2024]

As we discussed, I --

1. removed DecomposedMetric class,
2. kept only measure_run method in GlobalMetric class, and avoided extending Metric class.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.14%. Comparing base (61dc1b4) to head (cb59d1a).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #983      +/-   ##
==========================================
+ Coverage   88.96%   89.14%   +0.17%     
==========================================
  Files         218      218              
  Lines       15089    15012      -77     
==========================================
- Hits        13424    13382      -42     
+ Misses       1665     1630      -35     

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[mdekstrand]

Does RankingMetricBase inherit from ListMetric? Gini is not a listwise metric, so if it does then we should either:

• Make RankingMetricBase no longer inherit from ListMetric, and update all the ranking metrics that are listwise metrics to inherit from both RankingMetricBase and ListMetric.
• Rename RankingMetricBase to RankingListMetricBase and make GiniBase no longer inherit from RankingMetricBase
• A combination of the two: introduce RankingListMetricBase to be both ranking metric and list metric, and make the other metrics inherit from it.

[sushobhan2024]

RankingMetricBase inherits from Metric.