* chore_: unused `BuildTx` function removed from the processor interface and types that are implement it
Since the `BuildTx` function is not used anywhere, it's removed from the code.
* fix_: resolving nonce improvements
When the app sends more than a single tx from the same account on the same chain, some
chains do not return appropriate nonce (they do not consider pending txs), because of
that we place more tx with the same nonce, where all but the first one fail.
Changes in this PR keep track of nonces being used in the same sending/bridging flow, which means
for the first tx from the multi txs the app asks the chain for the nonce, and every next nonce is resolved
by incrementing the last used nonce by 1.
79b1c547d1