Improve parameter label fetching

[DanSava]

Issue User feedback for webviz-ert pointed out that if we are dealing with a case with numerous parameters there will be a lot of API calls to fetch possible parameter labels

Describe the solution you'd like Return parameter labels together with names when getting the ensemble parameters.

Describe alternatives you've considered

• Add API endpoint to retrieve all parameters together with labels if they exist.
• Update ensemble schema to accommodate not only parameter names but also possible labels

[markusdregi]

Related to: https://github.com/equinor/ert/issues/2838