Move adapter tests into their own module

[daffl]

It turned out to not be a great idea to have tests and utilities in the same repository. Since new modules are easy to add, the tests will be moved into their own module at @feathersjs/adapter-tests.

This also adds an additional test that makes sure a query with the id property of the service will throw an error. So something like:

app.service('messages').remove(1, { query: { id: 2 } });

Should fail if id is the id property because the id in the request and the query is not the same. This is important to e.g. secure a /users service easily by adding a query.