feat: add native balance in StorageChanges (#292)

* feat: add native balance in StorageChanges

This will be used by the next update of DCI to properly track native balance for all the contract that it's indexing. Also added a performance optimization, we now ignore slot updates if the value after the transaction is the same than before.

* docs: add docs on how to generate test assets

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Co-authored-by: zizou <111426680+flopell@users.noreply.github.com>

proto/tycho/evm/v1/common.proto

@@ -192,6 +192,8 @@ message StorageChanges {
   bytes address = 1;
   // The contract's storage changes
   repeated ContractSlot slots = 2;
+  // [optional] The contract's balance change
+  optional bytes native_balance = 3;
 }
 
 // Aggregate entities