annotate: move annotatepair unit tests to a separate file In upcoming patches the output is going to be significantly longer than it is today, and doctests don't allow wrapping the output. Differential Revision: https://phab.mercurial-scm.org/D896

check-code: allow an exception for camelcase where required unittest has a `maxDiff` parameter which has to be set to `None` in order for large enough failure diffs to be displayed. Add a comment to disable the camelcase check for `self.maxDiff = None` lines. Differential Revision: https://phab.mercurial-scm.org/D895