Revert "[analyzer] [NFC] Split up RetainSummaryManager from RetainCountChecker"

This reverts commit a786521fa66c72edd308baff0c08961b6d964fb1.

Bots haven't caught up yet, but broke modules build with:

../tools/clang/include/clang/StaticAnalyzer/Checkers/MPIFunctionClassifier.h:18:10:
fatal error: cyclic dependency in module 'Clang_StaticAnalyzer_Core':
Clang_StaticAnalyzer_Core -> Clang_Analysis ->
Clang_StaticAnalyzer_Checkers -> Clang_StaticAnalyzer_Core
         ^

llvm-svn: 340117