Migrate Old Keys To Registry

[winder]

Each time the node starts we should have a one-time check which looks for participation key files and imports them to the participation key registry. When finished the imported participation key files should be deleted.

This process should be pretty much identical to node.loadParticipationKeys(), but it runs once and deletes the files when finished.

Acceptance criteria

Use e2e go framework to test that keys are updated on startup