"Imagine" routes that fail #213
Description
When changing settings, it should still be possible to use the same route from before, adding it to the solve trie, so even though we cannot fully replay it into the queue, we should have a path we already know we can (at least partially) take further.
This has weird implications for certain rules and may lead to having impossible observations in the solve trie... at least until we trim them out. Which leads to the second question of whether we should keep the imagined routes in the solve trie.