build: switch playground examples to bazel (#28490)

Currently all playground examples are built with `tsc`
and served with the `gulp serve` task. In order to be able
to test these examples easily with Ivy, we now build and
serve the examples using Bazel. This allows us to expand our
Ivy test coverage and additionally it allows us to move forward
with the overall Bazel migration. Building & serving individual
examples is now very easy and doesn't involve building everything
inside of `/modules`.

PR Close #28490

modules/playground/src/sourcemap/BUILD.bazel

@@ -0,0 +1,34 @@
+load("//tools:defaults.bzl", "ng_module")
+load("@build_bazel_rules_typescript//:defs.bzl", "ts_devserver")
+
+package(default_visibility = ["//modules/playground:__subpackages__"])
+
+# Exported since the e2e test needs to read the source file in order to
+# ensure that the source map properly maps back to the source file.
+exports_files(["index.ts"])
+
+ng_module(
+    name = "sourcemap",
+    srcs = glob(["**/*.ts"]),
+    tsconfig = "//modules/playground:tsconfig-build.json",
+    # TODO: FW-1004 Type checking is currently not complete.
+    type_check = False,
+    deps = [
+        "//packages/core",
+        "//packages/platform-browser",
+        "//packages/platform-browser-dynamic",
+    ],
+)
+
+ts_devserver(
+    name = "devserver",
+    entry_module = "angular/modules/playground/src/sourcemap/index",
+    index_html = "index.html",
+    port = 4200,
+    scripts = ["@ngdeps//node_modules/tslib:tslib.js"],
+    static_files = [
+        "@ngdeps//node_modules/zone.js:dist/zone.js",
+        "@ngdeps//node_modules/reflect-metadata:Reflect.js",
+    ],
+    deps = [":sourcemap"],
+)

modules/playground/src/sourcemap/index.html

@@ -10,7 +10,5 @@
   Please look into the console and check whether the stack trace is mapped
   via source maps!
   </p>
-
-  <script src="../bootstrap.js"></script>
 </body>
 </html>

modules/playground/src/sourcemap/index.ts

@@ -20,9 +20,7 @@ export class ErrorComponent {
 }
 
 @NgModule({declarations: [ErrorComponent], bootstrap: [ErrorComponent], imports: [BrowserModule]})
-class ExampleModule {
+export class ExampleModule {
 }
 
-export function main() {
-  platformBrowserDynamic().bootstrapModule(ExampleModule);
-}
+platformBrowserDynamic().bootstrapModule(ExampleModule);