Expose the detection context to ScopDetection users

  ScopDetection users are interested in the detection context and access
  these via different get-methods. However, not all information was
  exposed though the number of maps to hold it was increasing steadily.
  With this change only the detection contexts the rejection log and the
  ValidRegions set are mapped. The former is needed, the second could be
  integrated in the first and the ValidRegions set is only needed for the
  deterministic order of the regions.

llvm-svn: 249614