* Initialize the rayon threadpool with a new config for CPU-bound threads
* Verify proofs and signatures on the rayon thread pool
* Only spawn one concurrent batch per verifier, for now
* Allow tower-batch to queue multiple batches
* Fix up a potentially incorrect comment
* Rename some variables for concurrent batches
* Spawn multiple batches concurrently, without any limits
* Simplify batch worker loop using OptionFuture
* Clear pending batches once they finish
* Stop accepting new items when we're at the concurrent batch limit
* Fail queued requests on drop
* Move pending_items and the batch timer into the worker struct
* Add worker fields to batch trace logs
* Run docker tests on PR series
* During full verification, process 20 blocks concurrently
* Remove an outdated comment about yielding to other tasks
* Use a new channel for each batch
* Prefer the batch timer if there are also new batch requests
* Allow other tasks to run after each batch
* Label each batch worker with the verifier's type
* Rename Handle to ErrorHandle, and fix up some docs
* Check batch worker tasks for panics and task termination
* Use tokio's PollSemaphore instead of an outdated Semaphore impl
* Run all verifier cryptography on a blocking thread
Also use a new verifier channel for each batch.
* Make flush and drop behaviour consistent for all verifiers
* Partly fix an incorrect NU5 test
* Switch batch tests to the multi-threaded runtime
* Export all verifier primitive modules from zebra-consensus
* Remove outdated test code in tower-batch
* Use a watch channel to send batch verifier results
* Use spawn_blocking for batch fallback verifiers
* Spawn cryptography batches onto blocking tokio threads
* Use smaller batches for halo2
* Minor tower-batch cleanups
* Fix doc link in zebra-test
* Drop previous permit before acquiring another to avoid a deadlock edge case