Deprecation: #76101 - remove SoloFieldContainer 

See forge#76101

Description 

The render() method of the SoloFieldContainer class has been marked as deprecated. It is not used in core anymore.

Impact 

Using the method will trigger a deprecation log entry.

Affected Installations 

Instances with custom extensions that use render() from SoloFieldContainer.

Migration 

Use the render method from the ListOfFieldsContainer class.