Allow doctrine/persistence 2.x

[fruitwasp]

Q	A
Type	improvement
BC Break	yes
Fixed issues

Summary

Adds support for doctrine/persistence 2.x

[malarzm]

BC break in 2.x is a no go. But this is not a lost cause, IIRC migration plan for doctrine/common was for libraries to require 1.x || 2.x to allow smooth transition for the ecosystem. Sadly I never had time to fully grasp the idea but there are better informed people :) @greg0ire would you mind chiming in?

[greg0ire]

You're correct, || ^2.0 can be added on the stable branch, here is how you should probably do that: doctrine/orm#8158

After that, people will have an upgrade path, and you can drop the ^1.0 || part (and the weird code artefacts I added in #2150 ), like this: doctrine/orm#8166

[fruitwasp]

done; targets the 2.1.x branch now too. Thanks for the guidance

[malarzm]

Thanks @fruitwasp!