Revert r197076: "[objcmt] When emitting a remap file, use a json format
with the edit entries, instead of applying the changes"

(And also revert the follow-up r197086.)

This seems to have broken Linux builds, which were failing with the following:

/build/buildbot/osu8/clang-x86_64-linux-selfhost-rel/llvm.obj/Release+Asserts/lib/libclang.so:
error: undefined reference to
'clang::ento::objc_retain::CallEffects::getEffect(clang::ObjCMethodDecl const*)'
/build/buildbot/osu8/clang-x86_64-linux-selfhost-rel/llvm.obj/Release+Asserts/lib/libclang.so:
error: undefined reference to
'clang::ento::objc_retain::CallEffects::getEffect(clang::FunctionDecl const*)'
collect2: error: ld returned 1 exit status