SylvaWorkladClusters must define a list of SylvaUnitsReleaseTemplates

Currently, the SWC operator build a SUR custom resource relying on both

• A user provided SWC object
• A management cluster admin provided SURT object. This object is not explicitely defined in the SWC CRD

These SURT should be immutable in order to avoid a reconciliation which is not triggered by the user. In addition, SURT composition is a necessary feature , therefore, the SWC CRD must include a list of SURT explicitley chosen by the user

The merging process is the following

• SURT ValuesFrom are added in the final SUR based on the SURT order
• SURT Values are merged following the SURT order
• SylvaUnitsSource is merged following the SURT order

If no SURT list is provided, the default SURT is used

The issue is about

• Adding this field
• Adding codes
• Adding tests