Remove dependencies on deprecated packages

[kstierhoff]

• [x] reshape2 (melt/cast) -> dplytr::pivot_longer and pivot_wider
• [x] rgdal (writeOGR) -> sf::writeOGR
• [x] maptools
• [x] rgeos
• [ ] others

[kstierhoff]

Done for now. Will revisit when other deprecated dependencies are identified.