Add some initial deny for unused_imports and unused_variables

Additional unused variable fix on unix

Remove unused import on unix

Remove unused windows import

lib/runtime-core/src/codegen.rs

@@ -1,6 +1,6 @@
 use crate::{
     backend::RunnableModule,
-    backend::{sys::Memory, Backend, CacheGen, Compiler, CompilerConfig, Token},
+    backend::{Backend, CacheGen, Compiler, CompilerConfig, Token},
     cache::{Artifact, Error as CacheError},
     error::{CompileError, CompileResult},
     module::{ModuleInfo, ModuleInner},

lib/runtime-core/src/lib.rs

@@ -1,3 +1,4 @@
+#![deny(unused_imports, unused_variables)]
 #![cfg_attr(nightly, feature(unwind_attributes))]
 
 #[cfg(test)]