Revert "r364412 [ExpandMemCmp][MergeICmps] Move passes out of CodeGen into opt pipeline."

Breaks sanitizers:
    libFuzzer :: cxxstring.test
    libFuzzer :: memcmp.test
    libFuzzer :: recommended-dictionary.test
    libFuzzer :: strcmp.test
    libFuzzer :: value-profile-mem.test
    libFuzzer :: value-profile-strcmp.test

llvm-svn: 364416