Eliminating complex ZonedCBS ADT and reintroducing a CBS with zone summaries.  Removing the default “high” segment preference, that caused the CBS trees to unbalance, and isn’t required outside of EP.  Considerable reduction in code and speed up, now at parity with master on test xc/Release/gcbench -x 1234 amc
Reverting exhaustive search in SplayFindFirst and SplayFindLast since zoned CBS will use an accurate test on the CBS block zones property, and this code will never be exercised.
Simplifying the interface to CBSFindInZones.
Speeding up CBSFindInZones a bit.