EZP-22477: Make sure legacy kernel handlers are reset

Required when changing scope, for instance in ContentPreview.
EZP-22477: Fixed ConfigScopeListener test
EZP-22477: Added PreResetLegacyKernelEvent

Receives the LegacyKernel before reset.
EZP-22477: phpdoc

[ci skip]
Merge pull request #832 from ezsystems/EZP-22477-image_alias_in_preview

Fixed re-injection of settings upon scope change