Remove normalization of failed transactions

From @tbinetruy search, we can get the status of the tx by the receipt. But each time we access the tx receipt we request the node. This PR will add a _receipt field on the EthereumTransaction Model, and will modify the property to get the data from the db if it exists.

It will also modify the index_level function of the EthereumProvider to filter out failed txs and not index them.