Make container mandatory in aconfig_declarations.

Bug: 330354107
Test: Unit test and CI.

Ignore-AOSP-First: It is easier to detect all the missing ones in internal
master.
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:e916a2c758d2a95037d1d366e7cd0e10d241d510)
Merged-In: I4ab4271c67a35d0fdcc0b57c27260e29fb7dea56
Change-Id: I4ab4271c67a35d0fdcc0b57c27260e29fb7dea56

java/app_test.go

@@ -4382,6 +4382,7 @@ func TestAppFlagsPackages(t *testing.T) {
 		aconfig_declarations {
 			name: "bar",
 			package: "com.example.package.bar",
+			container: "com.android.foo",
 			srcs: [
 				"bar.aconfig",
 			],
@@ -4389,6 +4390,7 @@ func TestAppFlagsPackages(t *testing.T) {
 		aconfig_declarations {
 			name: "baz",
 			package: "com.example.package.baz",
+			container: "com.android.foo",
 			srcs: [
 				"baz.aconfig",
 			],