b2ea441dc1
This is mostly removing code and tests related to reading/writing the cache file on macOS and updating of tests. Aside from that, the most notable part is the change to `setAttributionString` to automatically prepend `__MOZCUSTOM__` when writing an attribution code. This is mostly done to make things simpler and cleaner in the majority of the tests, but seeing as `getAttributionString` is also aware of it, it seems like a generally nicer way to do this. Differential Revision: https://phabricator.services.mozilla.com/D197204