fix(ivy): support listing lazy route for project-root-relative entry point in ngtsc (#28542)

I don't know of any use of this API with a project-root-relative path
(i.e. the cli will always call it with an absolute path), but keeping
the API backwards compatible just in case.

PR Close #28542

packages/compiler-cli/src/ngtsc/routing/index.ts

@@ -9,3 +9,4 @@
 /// <reference types="node" />
 
 export {LazyRoute, NgModuleRouteAnalyzer} from './src/analyzer';
+export {entryPointKeyFor} from './src/route';