Update all protocol handlers to use NewHandler() instead of legacy
NewMultiHandler() compatibility wrapper. This enables proper context
cancellation, protocol-level logging, and session ID tracking.
Changes:
- Add context.Background() and session IDs to all handler creations
- Add log.Logger fields to CGGMP21Protocol and FROSTProtocol structs
- Use protocol.DefaultConfig() for handler configuration
- Update handler types from *MultiHandler to *Handler