refactor: remove sync_engine crate and related dependencies

- Removed the sync_engine crate from the workspace and its dependencies from Cargo.lock.
- Updated metric labels to reflect the removal of sync_engine.
- Cleaned up Cargo.toml files across the project to eliminate references to sync_engine.

This change streamlines the project structure and eliminates unused components, enhancing maintainability.

Author: michaelgpt

Cargo.lock

@@ -8,7 +8,6 @@ members = [
     "crates/lighthouse_compat",
     "crates/miner",
     "crates/actor_system",
-    "crates/sync_engine",
     "tests"
 ]
 

Cargo.toml

@@ -24,7 +24,6 @@ lighthouse_wrapper = { package = "lighthouse_wrapper", path = "../crates/lightho
 # workspace
 bridge = { package = "federation", path = "../crates/federation" }
 actor_system = { path = "../crates/actor_system" }
-sync_engine = { path = "../crates/sync_engine" }
 federation_v2 = { path = "../crates/federation_v2" }
 lighthouse_wrapper_v2 = { path = "../crates/lighthouse_wrapper_v2" }
 

app/Cargo.toml

@@ -2231,7 +2231,7 @@ impl MetricLabels {
 
     /// Standard migration phase labels
     pub const MIGRATION_PHASES: &'static [&'static str] = &[
-        "foundation", "actor_system", "sync_engine", "federation_v2", 
+        "foundation", "actor_system", "federation_v2", 
         "lighthouse_v2", "migration", "validation", "rollback_safety",
         "performance_verification", "final_validation"
     ];