fix(test): handle TxnHashNotFound in db-compat test

[kariy]

The db-compat test has been failing since #392 bumped bBockifier to v0.16.0-rc.0, which introduced a breaking change in TransactionExecutionInfo struct serialization.

The v1.6.0 test database contains traces in the old format that can no longer be deserialized, causing trace_transaction to return TxnHashNotFound instead of the trace data.

This updates the test to accept TxnHashNotFound as a valid (expected) outcome for that call. The provider returns None on deserialization failure as a backward-compatibility measure:

match self.0.get::<tables::TxTraces>(num) {
    Ok(Some(execution)) => Ok(Some(execution)),
    Ok(None) => Ok(None),
    // Treat decompress errors as non-existent for backward compatibility
    Err(DatabaseError::Codec(CodecError::Decompress(err))) => {
        warn!(tx_num = %num, %err, "Failed to deserialize transaction trace");
        Ok(None)
    }
    Err(e) => Err(e.into()),
}