Merging all fsm2oshd development into main branch

[ArcticSnow]

This PR is about bringing FSM2oshd export and simulation development to the main branch of TopoPyScale:

• export function
• renaming of files from topo_sim.py to sim_fsm.py or sim_fsm2oshd.py
• added downscaling method grid which downscale to every points of the DEM
• and other minor typos and fixes