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

tools/defaults.bzl

@@ -1,6 +1,6 @@
 """Re-export of some bazel rules with repository-wide defaults."""
 load("@build_bazel_rules_typescript//:defs.bzl", _ts_library = "ts_library")
-load("//packages/bazel:index.bzl", _ng_module = "ng_module")
+load("//packages/bazel:index.bzl", _ng_module = "ng_module", _ng_package = "ng_package")
 
 DEFAULT_TSCONFIG = "//packages:tsconfig-build.json"
 
@@ -9,7 +9,24 @@ def ts_library(tsconfig = None, **kwargs):
     tsconfig = DEFAULT_TSCONFIG
   _ts_library(tsconfig = tsconfig, **kwargs)
 
-def ng_module(name, tsconfig = None, **kwargs):
+def ng_module(name, tsconfig = None, entry_point = None, **kwargs):
   if not tsconfig:
     tsconfig = DEFAULT_TSCONFIG
-  _ng_module(name = name, tsconfig = tsconfig, **kwargs)
+  if not entry_point:
+    entry_point = "public_api.ts"
+  _ng_module(name = name, tsconfig = tsconfig, entry_point = entry_point, **kwargs)
+
+def ng_package(name, readme_md = None, license_banner = None, stamp_data = None, **kwargs):
+  if not readme_md:
+    readme_md = "//packages:README.md"
+  if not license_banner:
+    license_banner = "//packages:license-banner.txt"
+  if not stamp_data:
+    stamp_data = "//tools:stamp_data"
+
+  _ng_package(
+      name = name,
+      readme_md = readme_md,
+      license_banner = license_banner,
+      stamp_data = stamp_data,
+      **kwargs)