Convert plugin discovery to attributes

Sadly this requires 11.1 for entity types.
So postponing for now.

Hi,

Is this a duplicate of #3543079: Convert phpdoc doctrine plugin annotation to modern attributes → ?

Edit: or the opposite depending on creation date. I may have posted the comment in the wrong issue, sorry.

You are totally right.

I took a different approach using rector instead of manual conversion, so we can just ignore this MR.
I'll start from scratch on the other one.

penyaskito → closed merge request !50