Add compatibility test for materialized-views

[eerxuan]

Part of #26.

Category: core / collections

Add compatibility test coverage for the materialized-views feature.

Note: no test coverage exists yet.

[danielfrankcom]

As per offline discussion and #233, I don't think this is needed. The coverage should already be included by the tests for merge and out.

[eerxuan]

Comprehensive compatibility tests now exist beyond the smoke test; closing.

[eerxuan]

Reopening: this was closed in error. materialized-views is a distinct feature from views (see #26), and there is no materialized-view test coverage — the core/collections/views/ tests cover regular views only.

[eerxuan]

Closing as descoped. Reason: Descoped — same as $merge and $out (see #233).