feat(explore): Show confirmation modal if user exits Explore without saving changes (#19993)

* feat(explore): Show confirmation modal if user exits Explore without saving changes

* Fix calling cleanup func unnecessarily

* Fix comparing AdhocMetric instance with JSON object

* Replace sliceFormData with the initial form data

superset-frontend/src/explore/exploreUtils/formData.test.ts

@@ -16,7 +16,7 @@
  * specific language governing permissions and limitations
  * under the License.
  */
-import { sanitizeFormData } from './formData';
+import { sanitizeFormData, isEqualish } from './formData';
 
 test('sanitizeFormData removes temporary control values', () => {
   expect(
@@ -26,3 +26,25 @@ test('sanitizeFormData removes temporary control values', () => {
     }),
   ).toEqual({ metrics: ['foo', 'bar'] });
 });
+
+test('isEqualish', () => {
+  // considers null, undefined, {} and [] as equal
+  expect(isEqualish(null, undefined)).toBe(true);
+  expect(isEqualish(null, [])).toBe(true);
+  expect(isEqualish(null, {})).toBe(true);
+  expect(isEqualish(undefined, {})).toBe(true);
+
+  // considers empty strings are the same as null
+  expect(isEqualish(undefined, '')).toBe(true);
+  expect(isEqualish(null, '')).toBe(true);
+
+  // considers deeply equal objects as equal
+  expect(isEqualish('', '')).toBe(true);
+  expect(isEqualish({ a: 1, b: 2, c: 3 }, { a: 1, b: 2, c: 3 })).toBe(true);
+
+  // Out of order
+  expect(isEqualish({ a: 1, b: 2, c: 3 }, { b: 2, a: 1, c: 3 })).toBe(true);
+
+  // Actually  not equal
+  expect(isEqualish({ a: 1, b: 2, z: 9 }, { a: 1, b: 2, c: 3 })).toBe(false);
+});