[analyzer] [NFC] Split up RetainSummaryManager from RetainCountChecker - try #2
Turns out it can't be removed from the analyzer since it relies on CallEvent.
Moving to staticAnalyzer/core
Differential Revision: https://reviews.llvm.org/D51023
I added a missing dependency in CMakeFiles for ARCMigrate to fix build break in build bot (http://lab.llvm.org:8011/builders/clang-ppc64le-linux-multistage/)