[AdminBundle] AsMenuAdaptor attribute to easily define menu adaptors with custom priorities

[acrobat]

Q	A
Bug fix?	no
New feature?	yes
BC breaks?	no
Deprecations?	no
Fixed tickets

With the new attribute you can control the menu priority without the need to add a service definition for it.

#[AsMenuAdaptor(priority: 100)]
class MenuAdaptor implements MenuAdaptorInterface
{
//...
}