We have code for converting C/C++/Objc keywords that appear in protos
to convert them so that they can be compiled.
One of the things we need to be careful of is accidentally overriding methods
that Apple declares in NSObject. It turns out that we have run into issues
where we conflict with "hidden" methods in NSObject or methods added by
categories. method_dump.sh collects all of the methods we care about for
macOS and iOS and dumps them into objectivec_nsobject_methods.h which
is then included in objectivec_helpers.cc as part of the build.

Added a pile of tests to verify that conversions are happening as expected.