Nonce gaps endpoint

[sstanculeanu]

Changes

• added new endpoint for nonce gaps by sender "/pool/by-sender/nonce-gaps/:sender"
• small refactor to remove code duplicate + for further improvements. Now txCache returns a slice of entire wrapped transactions which have all the info needed(hashes, nonces, etc)
• now received wrapped txs from all txCaches are merged and sorted on apiTransactionProcessor

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In order to test the changes, the following steps are needed:

1. start a local testnet with this branch
2. clone elrond-txgen-go and update the following:
   • in cmd/txgen/config/config.toml, leave Scenarios = ["badNonce"], update ProxyServerURL with the port that your local proxy uses, optional update MintingValue to a smaller one
   • copy from the newly generated node/config/walletKey.pem(local testnet) one of the private keys and paste it into cmd/txgen/config/walletKey.Pem
   • alter badNonceSecnario.go file, HandleTransaction method in order to always send bad nonces with gaps(eg. on line 62 you can use b.sendersMap[tx.Sender] = nonceToUse + 3)
3. cd /cmd/txgen, go build and start txgen ./txgen --new-account --num-accounts 10
4. run ./scripts/badNonce.sh
5. make a Get request to the node: http://127.0.0.1:node-port/transaction/pool to get tx pool
6. copy one hash and get the tx details via http://127.0.0.1:node-port/transaction/your-hash
7. copy the tx sender and get nonce gaps from this new endpoint: http://127.0.0.1:node-port/transaction/pool/by-sender/nonce-gaps/your-sender(if the provided alter example is used, one who tests should see many gaps of 3 nonces)

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (feat/new-tx-api@4cf8fa1). Click here to learn what that means.
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