improve developer experience of generator extension symbols (#9690)

libs/tools/generator/extensions/src/index.ts

@@ -2,3 +2,8 @@ export * as history from "./history";
 export * as legacyPassword from "./legacy-password";
 export * as legacyUsername from "./legacy-username";
 export * as navigation from "./navigation";
+
+export { GeneratorHistoryService } from "./history";
+export { GeneratorNavigationService } from "./navigation";
+export { PasswordGenerationServiceAbstraction } from "./legacy-password";
+export { UsernameGenerationServiceAbstraction } from "./legacy-username";