build(docs-infra): update project structure to cli@9 10/12 (tsconfig.json) (#36015)

Update `tsconfig[.*].json`.
Also, all make necessary changes to ensure the example apps can be
successfully built with the new, stricter type-checking options.

PR Close #36015

aio/tools/examples/shared/boilerplate/testing/tsconfig.app.json

@@ -4,8 +4,12 @@
     "outDir": "../out-tsc/app",
     "types": []
   },
+  "files": [
+    "src/main.ts",
+    "src/polyfills.ts"
+  ],
   "include": [
-    "src/**/*.ts"
+    "src/**/*.d.ts"
   ],
   "exclude": [
     "src/test.ts",

aio/tools/examples/shared/boilerplate/testing/tsconfig.spec.json

@@ -1,7 +1,7 @@
 {
   "extends": "./tsconfig.json",
   "compilerOptions": {
-    "outDir": "../out-tsc/spec",
+    "outDir": "./out-tsc/spec",
     "types": [
       "jasmine",
       "node"