Restore TestGeoDataCoordinates' testFromStringDMS & testFromStringDM

Summary:
Those tests had been disabled due to running too long, given the high
number of permutations created.
A possible solution would be to run the test only on a random subset of
those. 5% on my machine results in 2 seconds of run, which might be more
acceptable.
Restored version additionally tests both C locale and system locale.

Test Plan: All tests pass

Reviewers: #marble, nienhueser, rahn

Differential Revision: https://phabricator.kde.org/D1995