Update FoundationToWeb tests

[karwa]

FoundationToWeb tests are (intentionally) tightly coupled to the Foundation.URL implementation. For instance:

1. It uses Foundation's test database of interesting input strings, which it then parses with Foundation.URL and checks the resulting components, before converting them. We could technically loosen this -- we don't actually care what Foundation's parser produces; we should just check that we can convert its result safely.

2. It checks that some questionable behaviour/bugs in Foundation.URL (like unescaped backslashes) don't lead to problems when converted to WebURL.

Since Foundation changed the implementation of URL to use the URLComponents parser, the above tests have been failing.

We're not allowing any dangerous conversions, so the implementation doesn't need to change (it's intentionally robust to Foundation implementation changes), but the tests expect specific behaviour from Foundation's URL parser which now needs to be conditional.