Fix some warnings on nightly Rust (#5668)

* Fix some warnings on nightly Rust

Cargo is warning about the usage of workspace dependencies where the
workspace declaration does not mention `default-features` but the
dependency mentions `default-features`, so this explicitly turns off
default features for `cranelift-codegen` at the workspace level and
removes the explicit `default-features = false` at the manifest levels.

* Explicitly enable default feature in wasmtime

* Enable another feature

cranelift/frontend/Cargo.toml

@@ -11,7 +11,7 @@ readme = "README.md"
 edition.workspace = true
 
 [dependencies]
-cranelift-codegen = { workspace = true, default-features = false }
+cranelift-codegen = { workspace = true }
 target-lexicon = { workspace = true }
 log = { workspace = true }
 hashbrown = { workspace = true, optional = true }