Refactor grouped queries in CgmesModel

[rcourtier]

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)

Does this PR already have an issue describing the problem?

No.

What kind of change does this PR introduce?

Refactoring.

What is the current behavior?

There is a lack of consistency in the methods of CgmesModel that fetch data based on a common object ID. The methods don't have a similar naming, nor do they have a similar signature, and nor are they implemented in the same way and in the same class.
For instance:

• ratioTapChangerTable (table points grouped by table) // groupedTransformerEnds (transformer ends grouped by transformer)
• PropertyBags ratioTapChangerTable(String tableId) // Map<String, PropertyBags> groupedTransformerEnds()
• ratioTapChangerListForPowerTransformer (caching is done in Context) // nonlinearShuntCompensatorPoints (caching is done in AbstractCgmesModel)

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

Grouped queries now are implemented in a more consistent way, with a similar naming, a similar signature and a similar implementation in AbstractCgmesModel with final caches.

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:

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
93.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud