Interleave CPU-heavy operations with I/O events in the sync service

[tomaka]

Fix #2209

Right now, if the sync service is verifying a warp sync proof, in the meanwhile it doesn't respond to any event anymore.
This causes queues of operations to grow in size, and thus in latency, which causes other kind of small problems to manifest.

This PR makes sure that the sync service processes events at a certain minimum rate by interleaving CPU-heavy operations with responding to events.

[mergify]

Automatically approving tomaka's pull requests. This auto-approval will be removed once more maintainers are active.

[github-actions]

twiggy diff report

Difference in .wasm size before and after this pull request.

---

 Delta Bytes │ Item
─────────────┼────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
       -4167 ┊ <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::hfb4c5951913870cd
       +4103 ┊ <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::h94180dc30396580a
       -3443 ┊ <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::h733cb794077df532
       +3230 ┊ smoldot_light_base::sync_service::standalone::Task<TPlat>::process_one_verification_queue::h30343c6c657d4d14
       -2303 ┊ smoldot_light_base::sync_service::standalone::Task<TPlat>::start_requests::h3264895ac85ea711
       +2290 ┊ smoldot_light_base::sync_service::standalone::Task<TPlat>::start_next_request::h9cfbbc752ef6b23e
       +1172 ┊ smoldot::trie::proof_verify::trie_node_info::h0b479b94d153e5c1
       -1172 ┊ smoldot::trie::proof_verify::trie_node_info::h723ba75b5cbe223d
        -494 ┊ <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::h8c5cb3e97ab97b8c
        +494 ┊ <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::hf21dcae13a697619
        +446 ┊ <futures_util::future::poll_fn::PollFn<F> as core::future::future::Future>::poll::h1d7968f5a03f5126
        -411 ┊ core::ptr::drop_in_place<core::future::from_generator::GenFuture<smoldot_light_base::sync_service::standalone::start_standalone_chain<smoldot_light_wasm::platform::Platform>::{{closure}}>>::haa7c6d8ff3b3e7ab
        -407 ┊ <futures_util::future::poll_fn::PollFn<F> as core::future::future::Future>::poll::hbd0534ce5ff75b87
        +325 ┊ <core::iter::adapters::map::Map<I,F> as core::iter::traits::iterator::Iterator>::try_fold::h29e6e3b999a10a12
        -325 ┊ <core::iter::adapters::map::Map<I,F> as core::iter::traits::iterator::Iterator>::try_fold::h5f66d5ed81e0af1b
        +283 ┊ <core::iter::adapters::map::Map<I,F> as core::iter::traits::iterator::Iterator>::fold::h7a2e50ebe0b44c90
        -283 ┊ <core::iter::adapters::map::Map<I,F> as core::iter::traits::iterator::Iterator>::fold::hd6c9759714b63b7d
        +257 ┊ <alloc::vec::Vec<T> as alloc::vec::spec_from_iter_nested::SpecFromIterNested<T,I>>::from_iter::hd3810be0be5cc2aa
        -257 ┊ <alloc::vec::Vec<T> as alloc::vec::spec_from_iter_nested::SpecFromIterNested<T,I>>::from_iter::hf997972f5c575e93
        +247 ┊ <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::h08c3638a3e837ad2
         -10 ┊ ... and 94 more.
       -1500 ┊ Σ [114 Total Rows]

[melekes]

😮