Add merge method to RunHistory + extract trajectory from RunHistory

[benjamc]

Add these methods to RunHistory in order to more conveniently use pSMAC. pSMAC currently has no way of merging the results and for post-hoc analysis it is also important to have the merged results. Might be addressed in #855 . No API changes required / does not break anything.

class RunHistory(...):
  ...
  @staticmethod
  def merge(runhistories: List[RunHistory]) -> RunHistory:
    ...

  def extract_trajectory(self) -> Trajectory:
    ...

Trajectory currently is List[TrajEntry] but I prefer the json format. #870 is related. See extract trajectory in deepcave.

• [ ] Use endtime to order configs.

Related: pSMAC.read