Consolidate RailsManager to use RailOutcome

[tgasser-nv]

I can see that IORails does need a manager-level envelope for the triggering rail and accumulated execution records, but it does not need another verdict representation. a cleaner shape would be:

  @dataclass(frozen=True)
  class RailResult:
      outcome: RailOutcome
      triggered_rail: str | None = None
      records: tuple[RailCallRecord, ...] = ()

      @property
      def is_safe(self) -> bool:
          return not self.outcome.is_blocked

then RailOutcome remains the source of truth.

Originally posted by @Pouyanpi in #2261 (comment)

[tgasser-nv]

Closing now #2286 is merged