Merge pull request #20227 from emberjs/bugfix-ts-4.9

[BUGFIX release] Fix unsafe internal cast for NativeArray

Author: chriskrycho

packages/@ember/array/index.ts

@@ -1958,7 +1958,7 @@ if (ENV.EXTEND_PROTOTYPES.Array) {
 
     if (isEmberArray(arr)) {
       // SAFETY: If it's a true native array and it is also an EmberArray then it should be an Ember NativeArray
-      return arr as NativeArray<T>;
+      return arr as unknown as NativeArray<T>;
     } else {
       // SAFETY: This will return an NativeArray but TS can't infer that.
       return NativeArray.apply(arr ?? []) as NativeArray<T>;

packages/@ember/object/core.ts

@@ -261,7 +261,7 @@ class CoreObject {
 
       /* globals Proxy Reflect */
       self = new Proxy(this, {
-        get(target: CoreObject & HasUnknownProperty, property, receiver) {
+        get(target: typeof this & HasUnknownProperty, property, receiver) {
           if (property === PROXY_CONTENT) {
             return target;
           } else if (