Cosmos/FTS/Test: add query tests for full text on collection navigation

The scenario is not supported end to end, as we can't effectively construct the container (due to wildcards not being supported for index paths). This means, we can't use our regular functional test infrastructure.

What we could do is build the container using Microsoft.Azure.Cosmos SDK, and then manually create DBContext and query scenarios. We can use parts of our test infra to get information about cosmos connection string etc.