feat: Add evm feature gate

- Move all evm code inside evm directory
- StrategyEncoder:
  - Kept StrategyEncoder trait but created a new one: EVMStrategyEncoder to implement encode_protocol_header (that is evm specific).
  - All StrategyEncoders implement both traits now
  - Renamed DefaultStrategySelector -> EVMStrategySelector
- RouterEncoder:
  - Created a RouterEncoder trait and a EVMRouterEncoder that implements it
- Moved utils inside evm directory as well
- Renamed config.json -> executor_addresses.json and moved it to a higher config directory
- Make alloy optional and dependent on the evm feature gate

--- don't change below this line ---
ENG-4075 <#DTT#>

src/encoding/config/executor_addresses.json

@@ -0,0 +1,8 @@
+{
+  "executors": {
+    "ethereum": {
+      "uniswap_v2": "0x5C2F5a71f67c01775180ADc06909288B4C329308",
+      "vm:balancer_v2": "0x543778987b293C7E8Cf0722BB2e935ba6f4068D4"
+    }
+  }
+}