Add label as optional arg to @override directive

[Samjin]

Add support for 2nd argument label for progressive @override directive.
Support federation v2.7.

[dariuszkuc]

Currently this lib allows you specify you own custom @link federation spec import -> this change does not account for this and will update directive definitions even if folks specifically target older versions of federation

[Samjin]

Currently this lib allows you specify you own custom @link federation spec import -> this change does not account for this and will update directive definitions even if folks specifically target older versions of federation

Had a brief discussion, the plan is to check if progressive override label would work with older fed version from composition. if not, we'll have to check fed version per directives to make sure they are correctly generated.