Use Nightly + Cranelift for dev, only fail on warnings in CI (#4388)

* Switch to nightly + cranelift

* Fail on warnings only in CI

* Fix check errors

* Don't use mold on Linux to fix CI

* Pin nightly toolchain and add default rustup components

* Fix another CI thing

* PR comment

Cargo.toml

@@ -218,10 +218,6 @@ todo = "warn"
 unnested_or_patterns = "warn"
 wildcard_dependencies = "warn"
 
-[workspace.lints.rust]
-# Turn warnings into errors by default
-warnings = "deny"
-
 [patch.crates-io]
 wry = { git = "https://github.com/modrinth/wry", rev = "f2ce0b0" }