With AUTO_CURSEFORGE provide option to overwrite/skip existing files from overrides

[itzg]

Enhancement Type

Improve an existing feature

Describe the enhancement

Discussed at https://discord.com/channels/660567679458869252/660567682751528981/1067297541525348352

• Default to overwriting existing files when extracting modpack's overrides
• Provide option to flip that and skip existing files