Improve transaction submission (#6599)

* Improve transaction submission

Before this pr the transaction pool validated each transaction, even if
the transaction was already known to the pool. This pr changes the
behavior to first check if we are already aware of a transaction and
thus, to only validate them if we don't know them yet. However, there is
still the possibility that a given transaction is validated multiple
times. This can happen if the transaction is added the first time, but
is not yet validated and added to the validated pool.

Besides that, this pr fixes the wrong metrics of gossiped transactions
in the network. It also moves some metrics to the transaction pool api,
to better track when a transaction actually is scheduled for validation.

* Make sure we don't submit the same transaction twice from the network concurrently

* Remove added listener call

* Feedback

* Ignore banned on resubmit