Extend PositionCodec unit tests, better code coverage
Summary:
The test never tested position increments larger than 1, as the positions
where divided by the docId. Multibyte (i.e. value >= 128) position
steps where completely omitted.
Use identical datasets in the functional tests and in the benchmarks.
Test Plan: ctest
Reviewers: Baloo, Frameworks, ngraham, astippich, poboiko, lbeltrame
Reviewed By: lbeltrame
Subscribers: kde-frameworks-devel
Tags: Frameworks, Baloo
Differential Revision: https://phabricator.kde.org/D17331