[BUG] eth_getTransactionCount() doesn't support pending block number.

[rrw-zilliqa]

As title; this makes it impossible (using some frameworks) to submit more than one txn per block - though in order to fix this properly you need to talk to the same seedpub all the time, which we will attempt to address by enabling session affinity.

A more principled solution will turn up in a ZIP and then be implemented in ZQ2.

[chetan-zilliqa]

Implemented in #3931 PR.

[mauromedda]

shipped on ZQ1 mainnet