ENH: allow default rng to accept a legacy RandomState

ENH: allow default rng to accept a legacy RandomState: a task in MiMo-V2.6-RL-harbor-code: MiMo-V2.6-RL Code (Harbor) (Harbor dataset). I maintain a downstream library that is going through the SPEC 7 (https://scientific-python.org/specs/spec-0007/) transition — moving from legacy…