Update tests for transformer reactive power control on three-winding transformers

[p-arvy]

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)

Does this PR already have an issue describing the problem?

No.

What kind of change does this PR introduce?

While working on the OLF-Knitro-Solver repository (PR16), we noticed that the test transformerReactivePowerControlT3wtTest was unstable and not very meaningful.

The test has been updated by adding a cycle to the toy network to better evaluate the reactive power control of the transformer on the three-winding branch.

What is the current behavior?

Test transformerReactivePowerControlT3wtTest is unstable.

What is the new behavior (if this is a feature change)?
The test is updated.

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

• Yes
• No

If yes, please check if the following requirements are fulfilled

• The Breaking Change or Deprecated label has been added
• The migration steps are described in the following section

What changes might users need to make in their application due to this PR? (migration steps)

Other information:

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

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

See analysis details on SonarQube Cloud