When resolving allOf examples, only keep one examples list

Created by: ottomata

#14 added fancy code to create a cartesian product of all possible list of examples and merge those.

This is cool, but I had some errors when actually merging examples like this in real schema repos. Perhaps something changed in json-schema-merge-allof, but it now required me to add a defaultResolver for non JSONSchema keywords that end up being passed to its mergeSchemas function. This could work, but I think the right thing to do is just to keep the root schemas examples above all else. This avoids having to recurse into the examples objects themselves and merge them.

This means that examples in $ref-ed fragment schemas will not be used, which I think is a more sensible behavior.

This undoes the examples merging added in #14

Bug: T270134