Add test to verify no options are being shadowed by top level options

This will catch any model updates where an operation is added that is being shadowed by a top level option.

When I added this test I actually found a failure:

```
AssertionError: Shadowing a top level option: cloudsearchdomain.suggest.query
```

So I've fixed that as part of this PR.

cc @kyleknap @danielgtaylor