[BUGFIX LTS] do not throw on stable elementId

When refactoring from observers to setters during the 3.11 release
(in 405d423), an apparently-transparent change caused a regression
around invocations of components including `elementId=...`. *Any*
rerender of the component which included `elementId` assignment now
triggered the assertion, rather than *only* changes which actually
updated the value of `elementId`, because all invocations strigger
a `set` on the property.

The simplest reproduction of this bug (given a component `foo-bar`):

    {{foo-bar
      elementId='stable'
      changingValue=this.fromBackingClass
    }}

Changing the value `fromBackingClass` on the backing class *always*
triggers the assertion, even though it is actually impossible for
it to change the `elementId` value, because the assertion in the
setter throws regardless of what the value is. (The observer-based
did not throw in the same conditions because it would not retrigger
when the observed key on the view did not change.)

The fix is to check equality between the passed `elementId` value
and the previously set value, and only throw if they differ.

Fixes #18147

(cherry picked from commit da8c466)

Author: chriskrycho

packages/@ember/-internals/glimmer/tests/integration/components/curly-components-test.js

@@ -109,6 +109,39 @@ moduleFor(
       }
     }
 
+    ['@test elementId is stable when other values change']() {
+      let changingArg = 'arbitrary value';
+      let parentInstance;
+      this.registerComponent('foo-bar', {
+        ComponentClass: Component.extend({
+          init() {
+            this._super(...arguments);
+            parentInstance = this;
+          },
+          changingArg: changingArg,
+        }),
+        template: '{{quux-baz elementId="stable-id" changingArg=this.changingArg}}',
+      });
+
+      this.registerComponent('quux-baz', {
+        ComponentClass: Component.extend({}),
+        template: '{{changingArg}}',
+      });
+
+      this.render('{{foo-bar}}');
+      this.assertComponentElement(this.firstChild.firstChild, {
+        attrs: { id: 'stable-id' },
+        content: 'arbitrary value',
+      });
+
+      changingArg = 'a different value';
+      runTask(() => set(parentInstance, 'changingArg', changingArg));
+      this.assertComponentElement(this.firstChild.firstChild, {
+        attrs: { id: 'stable-id' },
+        content: changingArg,
+      });
+    }
+
     ['@test can specify template with `layoutName` property']() {
       let FooBarComponent = Component.extend({
         elementId: 'blahzorz',

packages/@ember/-internals/views/lib/views/states/in_dom.js

@@ -22,8 +22,10 @@ const inDOM = assign({}, hasElement, {
         get() {
           return elementId;
         },
-        set() {
-          throw new EmberError("Changing a view's elementId after creation is not allowed");
+        set(value) {
+          if (value !== elementId) {
+            throw new EmberError("Changing a view's elementId after creation is not allowed");
+          }
         },
       });
     }