`cargo gpu remove`

• cargo gpu remove --shader-crate ../shader-crate-template: should remove the rustc_codegen_spirv install of said shader crate
• cargo gpu remove --all should competely remove the entire cache dir, which would cleanup old installations by old cargo-gpu versions as well

Open Questions:

• remove or clean?
• cargo gpu remove <rust_gpu_version> We don't have a standardized way to declare a shader crate or a rust-gpu version. This would also be nice to have for installing
• Should we prompt the user about uninstalling toolchains as well? Note that two installs can use the same toolchain version. We could check every other install on whether the toolchain is used and prompt the user if noone is using it, which could be made easier by having some metadata file per install with the toolchain cached in it (among other things).

Inizia dall’implementazione del comando cargo gpu e segui come vengono registrate le installazioni di shader-crate e la directory della cache. Definisci il comportamento di rimozione per uno shader crate denominato e per --all, compreso se rimuovere le toolchain inutilizzate. Il lavoro è completo quando entrambe le modalità di pulizia funzionano senza influire sulle installazioni o sulle toolchain condivise.