feat: implement in-memory storage backend

Author: meyer9

Cargo.lock

@@ -11,6 +11,9 @@ description = "ExEx to save and serve trie nodes to make proofs faster."
 [lints]
 workspace = true
 
+[features]
+test-utils = []
+
 [dependencies]
 reth-exex.workspace = true
 
@@ -31,3 +34,11 @@ async-trait.workspace = true
 eyre.workspace = true
 futures-util.workspace = true
 serde.workspace = true
+thiserror.workspace = true
+tokio.workspace = true
+
+# dev dependencies
+[dev-dependencies]
+tokio = { workspace = true, features = ["test-util", "rt-multi-thread", "macros"] }
+test-case.workspace = true
+futures.workspace = true