Revision 59a0ea5d19dd9a7814190a022d6bff89584490f0

EZP-29613: As a developer I want access to ContentType on Content to avoid re-loading it (#2444)

API:
* Initial simple addition of `Content->getContentType()` API
* Implement getContentType() on Core User & UserGroup object
* Add SPI method for multi load content types
* Improve PHP doc on SPI/Persistence/Content/Type
* Adapt content domain mappers to bulk load content types
* Add unit test for Legacy/Content/Type/Handler::loadContentTypeList()
* Change MemoryCachingHandler to correctly use loadContentTypeList() and not single load()
* Change to use Doctrine QueryBuilder to fix loadTypesDataList(), use it for all loads for test coverage and consistency
* Fix Legacy Search test to keep connection, also refactor to avoid duplication

API:
* Expose `ContentTypeService->loadContentTypeList()` in order to adapt for new loadContentListByContentInfo()

Usage in Core, aka get rid of ContentType load operations:
* Adapt FieldRenderingExtension to use Content->getContentType()
* Optimize FieldHelper and it's usage in ContentExtension
* Optimize RestExecutedView to use content->getContentType()