refactor(core): rename ngComponentDef to ɵcmp (#33088)

Component defs are not considered public API, so the property
that contains them should be prefixed with Angular's marker
for "private" ('ɵ') to discourage apps from relying on def
APIs directly.

This commit adds the prefix and shortens the name from
`ngComponentDef` to `cmp`. This is because property names
cannot be minified by Uglify without turning on property
mangling (which most apps have turned off) and are thus
size-sensitive.

Note that the other "defs" (ngDirectiveDef, etc) will be
prefixed and shortened in follow-up PRs, in an attempt to
limit how large and conflict-y this change is.

PR Close #33088

packages/platform-browser/test/testing_public_spec.ts

@@ -781,7 +781,7 @@ const bTok = new InjectionToken<string>('b');
 
           it('should use set up providers', fakeAsync(() => {
                // Keeping this component inside the test is needed to make sure it's not resolved
-               // prior to this test, thus having ngComponentDef and a reference in resource
+               // prior to this test, thus having ɵcmp and a reference in resource
                // resolution queue. This is done to check external resoution logic in isolation by
                // configuring TestBed with the necessary ResourceLoader instance.
                @Component({