Fix /qualitymetrics to return data in expected format

[yurishkuro]

Which problem is this PR solving?

• Follow up to Create a /quality-metrics endpoint #6608
• Resolves Create dummy /quality-metrics endpoint #6607

Description of the changes

• Remove intermediate data: element from the response
• Match response to what the UI expects
• Fix unit test that wasn't testing the output

How was this change tested?

• unit tests
• manual test with Make changes to allow for /api/quality-metrics to work jaeger-ui#2641

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.02%. Comparing base (23d2254) to head (e5f3b45).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6733      +/-   ##
==========================================
- Coverage   96.06%   96.02%   -0.04%     
==========================================
  Files         364      364              
  Lines       20696    20692       -4     
==========================================
- Hits        19881    19869      -12     
- Misses        622      628       +6     
- Partials      193      195       +2     

Flag	Coverage Δ
badger_v1	9.76% <ø> (ø)
badger_v2	1.82% <ø> (ø)
cassandra-4.x-v1-manual	14.81% <ø> (ø)
cassandra-4.x-v2-auto	1.81% <ø> (ø)
cassandra-4.x-v2-manual	1.81% <ø> (ø)
cassandra-5.x-v1-manual	14.81% <ø> (ø)
cassandra-5.x-v2-auto	1.81% <ø> (ø)
cassandra-5.x-v2-manual	1.81% <ø> (ø)
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elasticsearch-7.x-v1	19.23% <ø> (ø)
elasticsearch-8.x-v1	19.40% <ø> (ø)
elasticsearch-8.x-v2	1.82% <ø> (ø)
grpc_v1	10.81% <ø> (ø)
grpc_v2	7.80% <ø> (ø)
kafka-3.x-v1	10.13% <ø> (ø)
kafka-3.x-v2	1.82% <ø> (ø)
memory_v2	1.82% <ø> (ø)
opensearch-1.x-v1	19.28% <ø> (ø)
opensearch-2.x-v1	19.28% <ø> (ø)
opensearch-2.x-v2	1.82% <ø> (ø)
tailsampling-processor	0.48% <ø> (ø)
unittests	94.91% <100.00%> (-0.04%)	⬇️

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[jkowall]

Looks good, thanks.