Add support for Symfony 7 given removal of ContainerAwareInterface

[pieterocp]

Marking this as a draft since I'm not using the doctrine removal inside the project + might require some intermediary steps, e.g. a deprecation notice inside the library to make the upgrade path from 6.* -> 7.* easier.

[michnovka]

I went over the Symfony 7 docs and source code of EndlessContainerAwareCommand.

I think we should get rid of this class. Symfony 7 forces us to use dependency injection inside constructor, so if somebody wants to work with doctrine, they should in fact inject EntityManager in their own constructor of the derived class. Then they can call doctrine->clear() if they want it (not every use case does).

I propose to just remove this class and add a mention of this and above steps to UPGRADE file. WDYT @mac-cain13 ?

[mac-cain13]

Thanks for the contibution @pieterocp, will merge the PR from @michnovka to get this update in.