fix(material/autocomplete): prevent outside clicks from going to other overlays

Adds a subscription to the outside click stream of the autocomplete overlay so that the events don't propagate to other overlays which may close the autocomplete prematurely.

Fixes #25238.

Author: crisbeto

integration/harness-e2e-cli/e2e/radio-harness.spec.ts

@@ -7,22 +7,30 @@ describe('app test', () => {
   let loader: HarnessLoader;
 
   beforeEach(async () => {
+    console.log('starting');
     const driver = await configureDriver();
 
     await driver.get('http://localhost:4200');
+    console.log('loaded');
 
     loader = SeleniumWebDriverHarnessEnvironment.loader(driver);
   });
 
   it('should work', async () => {
+    console.log('test start');
     const group = await loader.getHarness(MatRadioGroupHarness);
+    console.log('group loaded');
 
     expect(group).toBeDefined();
     expect(await group.getCheckedValue()).toBe(null);
+    console.log('initial value');
 
     const buttons = await group.getRadioButtons();
+    console.log('fetched buttons');
     await buttons[1].check();
+    console.log('checked');
 
     expect(await group.getCheckedValue()).toBe('second');
+    console.log('asserted');
   });
 });

src/material/autocomplete/autocomplete-trigger.ts

@@ -836,6 +836,11 @@ export abstract class _MatAutocompleteTriggerBase
         event.preventDefault();
       }
     });
+
+    // Subscribe to the pointer events stream so that it doesn't get picked up by other overlays.
+    // TODO(crisbeto): we should switch `_getOutsideClickStream` eventually to use this stream,
+    // but the behvior isn't exactly the same and it ends up breaking some internal tests.
+    overlayRef.outsidePointerEvents().subscribe();
   }
 }