feat(vm): Do not panic on VM divergence (#2705)

## What ❔

- Allows to continue batch execution on divergence via new
`ShadowLenient` VM mode.
- Dumps VM state to logs and optionally a file on divergence.

## Why ❔

Allows to detect divergencies in multiple batches w/o blockers. The
dumped VM state will hopefully allow investigating divergencies locally,
although this logic isn't implemented yet.

## Checklist

- [x] PR title corresponds to the body of PR (we generate changelog
entries from PRs).
- [x] Tests for the changes have been added / updated.
- [x] Documentation comments have been added / updated.
- [x] Code has been formatted via `zk fmt` and `zk lint`.

Author: slowli

Cargo.lock

@@ -32,8 +32,9 @@ pub enum FastVmMode {
     /// Run only the old VM.
     #[default]
     Old,
-    /// Run only the new Vm.
+    /// Run only the new VM.
     New,
     /// Run both the new and old VM and compare their outputs for each transaction execution.
+    /// The VM will panic on divergence.
     Shadow,
 }

core/lib/basic_types/src/vm.rs

@@ -34,13 +34,13 @@ anyhow.workspace = true
 hex.workspace = true
 itertools.workspace = true
 once_cell.workspace = true
-pretty_assertions.workspace = true
 thiserror.workspace = true
 tracing.workspace = true
 vise.workspace = true
 
 [dev-dependencies]
 assert_matches.workspace = true
+pretty_assertions.workspace = true
 tokio = { workspace = true, features = ["time"] }
 zksync_test_account.workspace = true
 ethabi.workspace = true

core/lib/multivm/Cargo.toml

@@ -22,5 +22,5 @@ pub use crate::{
 mod glue;
 pub mod tracers;
 pub mod utils;
-pub mod versions;
+mod versions;
 mod vm_instance;

core/lib/multivm/src/lib.rs

@@ -1,5 +1,8 @@
-pub mod shadow;
 mod shared;
+#[cfg(test)]
+mod testonly;
+#[cfg(test)]
+mod tests;
 pub mod vm_1_3_2;
 pub mod vm_1_4_1;
 pub mod vm_1_4_2;