Refactor DistributedSlackOuterLoop reports when handling several SC

[bperr]

Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• A PR or issue has been opened in all impacted repositories (if any)

What kind of change does this PR introduce?

Minor feature change, not covered in the last PR : clean reports for distributed slack outer loop when there are several SC

What is the current behavior?

Report structure is

+ Outer loop DistributedSlack
   + SC0
      + Outer loop iteration 1
         Slack bus active power (40 MW) distributed in 1 distribution iteration(s)
   + SC1
      + Outer loop iteration 1
         Slack bus active power (-19.998222 MW) distributed in 1 distribution iteration(s)

What is the new behavior (if this is a feature change)?
New structure is

+ Outer loop DistributedSlack
   + Outer loop iteration 1
      + SC0
         Slack bus active power (40 MW) distributed in 1 distribution iteration(s)
      + SC1
         Slack bus active power (-19.998222 MW) distributed in 1 distribution iteration(s)

Please not that a SC is not added if there is no report inside.

Does this PR introduce a breaking change or deprecate an API?

• Yes
• No

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
95.8% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[SylvestreSakti]

Thank you for solving this !