Rely on new ES mapping contribution

Since LTS 2021.17, the platform team introduced a new contribution to append mapping definition to existing ES index (NXP-30539). We want to update the feature in Modeler to generate the proper contributions in the build of the project in order to append the mappings defined in Studio.

Changes required:

• Add a new text field on each ESMapping feature to define the name of the index for which the mapping is defined, it should have a default value 'nuxeo'
• At build, group the features by index name and generate a JSON file per index with a different name for each file
• Generate the contributions in the extensions.xml output file referencing the previously generated JSON files
• Add a warning in Modeler that the feature is only available from LTS 2021.17
• When in LTS 2021, remove the existing button to generate a JSON file with all the mappings
• In the container page listing the created mappings, add a new column with the index name (only in LTS 2021 and after)