chore: minor cleanup in icon tests and virtual scrolling (#11481)

* Removes a file that wasn't being used for anything under `cdk-experimental/scrolling`.
* Enables `strictMetadataEmit` for the scrolling package.
* Fixes a test for the icons which was leaking out a warning message.

Author: crisbeto

src/lib/icon/icon.spec.ts

@@ -428,9 +428,9 @@ describe('MatIcon', () => {
     }));
 
     it('should throw an error when using untrusted HTML', () => {
-      // Stub out console.error so we don't pollute our logs with Angular's warnings.
+      // Stub out console.warn so we don't pollute our logs with Angular's warnings.
       // Jasmine will tear the spy down at the end of the test.
-      spyOn(console, 'error');
+      spyOn(console, 'warn');
 
       expect(() => {
         iconRegistry.addSvgIconLiteral('circle', '<svg><circle></svg>');