[BUGFIX stable] Allow store to be injected on Route

In the public types, TypeScript (correctly) complains when users try to
inject the store with `@service store` on a `Route` subclass, because
the item is an accessor on `Route` itself, and the service injection
"happens" to work only because the `set store(value)` smashes itself as
well as the corresponding `get store()` using `defineProperty`.

Work around this by renaming the getter in question to `_store` and
updating the one usage to check for a `store` property before falling
back to the `_store` property. Happily, this also dovetails with the
plan to deprecate the automatic `findModel` behavior this exists to
support: once that is removed, this entire code path can be cleaned up
trivially.

packages/@ember/routing/route.ts

@@ -1234,7 +1234,13 @@ class Route<Model = unknown> extends EmberObject.extend(ActionHandler, Evented)
     @private
   */
   findModel(...args: any[]) {
-    return (get(this, 'store') as any).find(...args);
+    // SAFETY: it's all absurd lies; there is no explicit contract for `store`
+    // and we allow people to register *anything* here and we call it: GLHF! The
+    // fallback path here means we correctly handle the case where there is no
+    // explicit store injection on the route subclass.
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    let store = ('store' in this ? this.store : get(this, '_store')) as any;
+    return store.find(...args);
   }
 
   /**
@@ -1573,7 +1579,7 @@ class Route<Model = unknown> extends EmberObject.extend(ActionHandler, Evented)
     @private
   */
   @computed
-  protected get store() {
+  protected get _store() {
     const owner = getOwner(this);
     assert('Route is unexpectedly missing an owner', owner);
     let routeName = this.routeName;
@@ -1620,10 +1626,6 @@ class Route<Model = unknown> extends EmberObject.extend(ActionHandler, Evented)
     };
   }
 
-  protected set store(value: any) {
-    defineProperty(this, 'store', null, value);
-  }
-
   /**
     @private
     @property _qp

tests/docs/expected.js

@@ -484,7 +484,7 @@ module.exports = {
     'sort',
     'sortBy',
     'startRouting',
-    'store',
+    '_store',
     'subscribe',
     'sum',
     'tagName',