Describes an observed parent-child relationship in an OTP supervision tree.
A child ID can be absent when the supervisor reports a child specification without a currently running process.
@type t() :: %BeamConsole.SupervisionEdge{ child_id: String.t() | nil, child_type: :supervisor | :worker | nil, id: String.t(), label: String.t(), parent_id: String.t(), state: :running | :restarting | :undefined | :missing }