Use full APIs for api_lint.new_since of *api-stubs-docs-non-updatable

Previously, the `*api-stubs-docs-non-updatable` modules used either the
full previously released public API or a delta for those API surfaces
that extend another API surface. Just passing a delta meant that lint
would not be able to properly ignore issues that already existed in
previously released APIs.

This change switches them to use the `*.api.combined.*.latest` modules
which contains the full API for each surface, including the API
provided by any API surface it extends. That ensures that lint will
not report issues with previously released APIs.

Bug: 341078916
Test: m checkapi
      # Check that multiple --api-lint-previous-api options are passed
      # to metalava for system-api-stubs-docs-non-updatable
Change-Id: I8a6d1263086466fda111266fe8bfdfedf0f8c152