Compatibility with preCICE v3

[MakisH]

At some point in the next year, preCICE v3 is coming. We need to update the adapter accordingly.

Changes to consider:

• [x] Drop issue https://github.com/precice/openfoam-adapter/issues/3
• [x] Merged initializeData into intialize: https://github.com/precice/precice/pull/1350 -> Solved by #266.
• [x] Updated connectivity API (adjust setMeshEdges and setMeshTriangles to use vertex IDs): https://github.com/precice/precice/pull/1322, https://github.com/precice/precice/issues/1321 -> Solved by #297.
• [x] Updated actions/checkpointing API: https://github.com/precice/precice/issues/719 -> Solved by #285
• [ ] Unsigned sizes: https://github.com/precice/precice/issues/405
• [ ] (additional) Exiting the coupling earlier, if needed: https://github.com/precice/precice/issues/1118
• [x] Apply any waveform iteration related changes needed. -> Solved by #285.