feat(engine): wire StateRootTask in EngineApiTreeHandler

[fgimenez]

Towards #12053

[gakonst]

is this expected to instantiate a state root task each time, or is it expected that we spawn it once?

[fgimenez]

yep, it is designed to instantiate one task per block. maybe we could get rid of the overhead of creating the task with a background service, similar to what we have for persistence, once everything is working correctly we can measure to compare both approaches

[rkrasiuk]

why is this necessary?

[fgimenez]

without it there are issues with the lifecycle of the variables used inside the std::thread::scope, even when they are created outside it, bc of the state hook being moved outside the scoped thread. the errors look like this:

error[E0597]: `provider_ro` does not live long enough
    --> crates/engine/tree/src/tree/mod.rs:2264:56
     |
2255 |         let provider_ro = consistent_view.provider_ro()?;
     |             ----------- binding `provider_ro` declared here
...
2260 |         let state_root_result = match std::thread::scope(|scope| {
     |                                                          ------- value captured here
...
2264 |                         DatabaseTrieCursorFactory::new(provider_ro.tx_ref()),
     |                                                        ^^^^^^^^^^^ borrowed value does not live long enough
...
2277 |                 (Some(state_root_task.spawn(scope)), Box::new(state_hook) as Box<dyn OnStateHook>)
     |                                                      -------------------------------------------- cast requires that `provider_ro` is borrowed for `'static`
...
2419 |     }
     |     - `provider_ro` dropped here while still borrowed