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