fix(filterFilter): let expression object `{$: '...'}` also match primitive items

Closes #10428
This test is supposed to fail (in a sane world), because there is an inherited property (`someProp: 'oo'`). So, `{$: 'll'}` in this case, should be equivalent with `{$: 'll', someProp: 'oo'}`, which in turn (in a sane world again) means: _Match any object that has a property named `someProp` and whose value is a superstring of `oo` and has any property whose value is a superstring of `ll`._

And because there is no such property, 0 items should be returned.

But...