[reporting] Group unused skips by rule, skip reporting on narrowed runs

[TomasVotruba]

Unused skip reporting: group by rule + avoid false positives

Follow-up to the unused-skip reporting feature.

Group unused paths by rule

Previously each unused rule-scoped skip was printed on its own line, repeating the rule class:

* Rector\...\ReturnTypeFromReturnDirectArrayRector => app/bundles/LeadBundle/Model/LeadModel.php
* Rector\...\ReturnTypeFromReturnDirectArrayRector => app/bundles/CoreBundle/Entity/TranslationEntity.php

Now multiple paths are grouped under their rule, matching the ->withSkip() config shape:

* Rector\...\ReturnTypeFromReturnDirectArrayRector => [ app/bundles/LeadBundle/Model/LeadModel.php
    app/bundles/CoreBundle/Entity/TranslationEntity.php ]

Single-path skips stay on one line as before.

Skip reporting on narrowed runs

A narrowed run only touches part of the codebase, so skips outside that scope look falsely unused and produce many false positives. Unused-skip reporting is now disabled when the run is narrowed via:

• a CLI paths argument (e.g. bin/rector process app/bundles/PointBundle/Controller/TriggerController.php)
• --only
• --only-suffix

This applies to both console and JSON output (both go through UnusedSkipResolver).