feat(bazel): add an ng_package rule (#22221)

This produces a directory following the Angular Package layout spec.

Includes integration test coverage by making a minimal ng_package in integration/bazel.
Unit tests verify the content of the @angular/core and @angular/common packages.

This doesn't totally match our current output, but is good enough to unblock some
early adopters.

It re-uses logic from the rollup_bundle rule in rules_nodejs. It should also
eventually have the .pack and .publish secondary targets like npm_package rule.

PR Close #22221

packages/compiler-cli/integrationtest/bazel/ng_module/BUILD.bazel

@@ -3,6 +3,7 @@ load("//packages/bazel:index.bzl", "ng_module")
 ng_module(
     name = "test_module",
     srcs = glob(["*.ts"]),
+    entry_point = "index.ts",
     module_name = "some_npm_module",
     deps = ["//packages/core"],
 )