[VnV][telemac3d] Update pildepon example with better choices for a few keywords

- TREATMENT OF NEGATIVE DEPTHS = 2 (new default value since release 9.0)
to improve mass conservation of water (already chosen for NH example)
- use of default advection scheme for velocities (LIPS): better parallelisation
than with method of characteristics
- use of gradient conjugate to solve PPE (little bit more efficient)

Add comparison of the advection of tracers with PC1/PC2/LIPS

Same time step for non-hydrostatic and hydrostatic versions (now = 0.4 s as NH
before)