bookmark: also make bookmark cache depends of the changelog
Since the changelog is also used during the parsing of bookmark data, it should
be listed as a file cache dependency. This fix the race condition we just
introduced a test for.
This is a simple fix that might lead bookmark data to be invalidated more often
than necessary. We could have more complicated code to deal with this race in a
more "optimal" way. I feel it would be unsuitable for stable.
In addition, the performance impact of this is probably minimal and I don't
foresee the more advanced fix to actually be necessary.