Fix optimistic updates

[dfahlander]

The unit tests for dexie-react-hooks failed. This PR resolves the failures that happened and makes the test work simpler by also functioning in cache mode (when the liveQueries updates immediately).

The issues found in dexie's liveQuery and cache-middleware was the following:

• useObservable() will launch the querier immediately on component render to test if it could give out a synchronous value. This is generic code in order to support synchronous observables but isnt' very good with liveQuery observable since useLiveQuery() uses useObservable(liveQuery()) internally and useObservable() forces it to run a dummy query on every initial render of a component. This is optimized to not do that by inspecting hasValue() of the observable and if that function is present and returning false, don't care to try getting a synchronous value.
• The above behavior in combination with that we now abort the transaction when unsubscribing, caused the cache to store a failing promise.
• When the querier is executed next time (to actually care about what's coming), it will find the cached promise and wait for it (it doesn't know quite yet that it will be failing with AbortError). When it eventually fails, the valid liveQuery fails and the component throws and the ErrorBoundary is shown.
• Tried to workaround this by re-executing the query in case it was from the cache and fails. Still got error, this time Transaction is inactive. Turned out the reason for this is that the original transaction was lost while waiting for the promise in the cache (that eventually failed). So we actually had to launch a new and fresh readonly transaction when this happens. This solved the entire issue.
• Then, I also optimized so that useObservable doesn't try to subscribe to liveQuery observables immediately, but instead waits until the effect is launched and only fires queries towards indexedb when they are actually being observed.

I have also a corresponding PR for master-3 (dexie@3.x) that enables the hasValue() method on returned observables so that the next version of dexie-react-hooks will optimize also for dexie@3.