Allow default visibility to be set per package

Adds a package module type with a default_visibility property. The
package module type can only be specified once per package.

Bug: 133290645
Test: m droid
Change-Id: Ibb2fb499c9ea88ecaa662d3cd2cbde478e4b9a4b

Android.bp

@@ -58,6 +58,7 @@ bootstrap_go_package {
         "android/notices.go",
         "android/onceper.go",
         "android/override_module.go",
+        "android/package.go",
         "android/package_ctx.go",
         "android/path_properties.go",
         "android/paths.go",
@@ -88,6 +89,7 @@ bootstrap_go_package {
         "android/namespace_test.go",
         "android/neverallow_test.go",
         "android/onceper_test.go",
+        "android/package_test.go",
         "android/path_properties_test.go",
         "android/paths_test.go",
         "android/prebuilt_test.go",