Query state enum refactor + Fixing Cache Cleanup

[nicoburniske]

Relatively large refactor to address #2

• Boolean signals inside of Query are now replaced with QueryState enum. Stale is intentionally not a state, and is instead a derived signal inside of QueryResult. This distinction allows for a query to be stale, while also having a descriptive state.

pub enum QueryState<V> {
    /// The initial state of a Query upon its creation.
    Created,

    /// Query is fetching for the first time.
    Loading,

    /// A Query is in the process of fetching, not being its first fetch.
    Fetching(QueryData<V>),

    /// The state indicating that a query has successfully completed a fetch operation.
    Loaded(QueryData<V>),

    /// The state indicating that a query has completed a fetch, but the fetched data is marked as invalid.
    Invalid(QueryData<V>),
}

• Prevent effect nesting where possible in query_executor
• Fix ensure_cache_cleanup to have non-duplicate timeouts, cleanups, and prevent disposing of Query while in use
  • Query Eviction from Cache will not happen until Query is no longer active.
• Refactor QueryResult
  • Refetch is now Fn() + Clone instead of SignalSetter<()>
  • QueryResult<V> now contains a QueryState<V>
  • Removed Signal for updated_at
• Removed QueryClient::get_query_data due to inconsistent behavior.