Port the source and test-utils changes required by the reth 1.11.1 /
Tsuki upgrade (mirrors scroll-tech/rollup-node scroll-tech#500):

- Migrate off the removed spawn / spawn_critical task helpers. pprof
  stays critical via spawn_critical_task; db_maintenance and
  scroll_network_manager use spawn_task to preserve their original
  non-critical behavior (a plain rename to spawn_critical_task would
  silently tear down the node if the network manager returns).
- Implement RpcHandleProvider::rpc_handle_mut on ScrollAddOnsHandle.
- Replace TaskManager with TaskExecutor in the node test harness, and
  build it with TaskExecutor::test() (lightweight 2-thread pools) rather
  than ::default(), which would allocate full CPU-sized pools per node
  and blow up thread counts on high-core CI under --all-features. Move
  the graceful-shutdown closure accordingly.
- Rename TransactionTestContext::transfer_tx_nonce_bytes to
  transfer_tx_bytes_with_nonce.
- Update the sequencer setup() call sites to the new 2-tuple return.
- Regenerate anvil_state.json for the newer anvil serialization
  (adds gas_refund_counter).
- Test stabilizers: bump txpool max_account_slots (with rationale),
  tolerate already-known transactions, wait on block_sequenced instead
  of a fixed sleep, raise integration timeouts to 120s, and run nextest
  with --test-threads 4.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Port the source and test-utils changes required by the reth 1.11.1 /
Tsuki upgrade (mirrors scroll-tech/rollup-node scroll-tech#500):

- Migrate off the removed spawn / spawn_critical task helpers. pprof
  stays critical via spawn_critical_task; db_maintenance and
  scroll_network_manager use spawn_task to preserve their original
  non-critical behavior (a plain rename to spawn_critical_task would
  silently tear down the node if the network manager returns).
- Implement RpcHandleProvider::rpc_handle_mut on ScrollAddOnsHandle.
- Replace TaskManager with TaskExecutor in the node test harness, and
  build it with TaskExecutor::test() (lightweight 2-thread pools) rather
  than ::default(), which would allocate full CPU-sized pools per node
  and blow up thread counts on high-core CI under --all-features. Move
  the graceful-shutdown closure accordingly.
- Rename TransactionTestContext::transfer_tx_nonce_bytes to
  transfer_tx_bytes_with_nonce.
- Update the sequencer setup() call sites to the new 2-tuple return.
- Regenerate anvil_state.json for the newer anvil serialization
  (adds gas_refund_counter).
- Test stabilizers: bump txpool max_account_slots (with rationale),
  tolerate already-known transactions, wait on block_sequenced instead
  of a fixed sleep, raise integration timeouts to 120s, and run nextest
  with --test-threads 4.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>