Extract transaction into blockchain_transaction

[unnawut]

Is your feature request related to a problem? Please describe.

Currently we have EWalletDB.Transaction containing some local information as well as blockchain information. We're also about to have EWalletDB.DepositTransaction, etc. which means a lot of blockchain info will be duplicated in the database.

Describe the solution you'd like

The idea is to consolidate blockchain transaction info into EWalletDB.BlockchainTransaction so there's only a single source of truth and keeping separation of concern between transactions and blockchain transactions.

This also means that EWalletDB.TransactionState will also need to be refactored, but will pave way for simpler state machines.

Additional context

In @mederic-p's own words:

I’m starting to think that we should have a new blockchain_transaction table with the following fields (at least):

• :status
• :blockchain_tx_hash
• :blockchain_identifier
• :confirmations_count
• :blk_number
  So we can reference this blockchain transaction in the tables that need it. For now we store these fields directly in the tables but we will have a lot of duplicates. We will need it for at least transaction (when creating a blockchain transaction), token when deploying an erc20 token, mint when minting a token, maybe more.
  This will also allow an entity to reference multiple blockchain transactions. A token that we create will have a creation_blockchain_tx_id and can also have a reference to a middle table for all its minting_blockchain_tx and can have a finish_minting_blockchain_tx_id.

Inputs from @T-Dnzt:

Both ethereum and plasma transactions go into blockchain_transaction table

token and mint need to be refactored to contain only blockchain_transaction_uuid reference

Deposit transactions do need to exist because they contain logic that doesn't belong in a generic blockchain transaction table, to show the list of all deposit transactions happening and if it's going in or out to/from the hot wallet.