`alias Foo.{Bar, Baz}` (and the same import/require/use brace form) emitted
NO imports edges. tree-sitter-elixir represents it as a `dot` node holding the
base alias plus a trailing `tuple` of member aliases, but the import handler
only matched a bare `alias` child, so every multi-alias import was silently
dropped.
Add `_get_alias_modules`, which expands the brace form to `Foo.Bar`,
`Foo.Baz`, … while leaving the single form (`alias Foo.Bar`) unchanged. Adds a
fixture line + regression test.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
