Refactor `sender` pre-conditions to avoid checking genesis about polkadot-stps HOT 2 CLOSED

we originally chose genesis but it's not a hard requirement

it's actually not ideal, depending on how you look at it (we want to check pre-conditions immediately before the benchmarking starts, not a long time ago)

this can be easily achieved by changing this:

where genesis can be simply replaced with head and the effect would be the same

from polkadot-stps.

The above would work for relaychains specifically, but when we target parachains things would again get a bit more complicated since we need to check the last parachain block.
The quick fix which comes to my mind is simply doing what we do in tps, passing the latest para head to the parachain subxt client and checking the accounts from the last included parablock.

Edit
Actually, not sure if it is possible to check the accounts in the parablock in the same way exactly. If it is, then I suspect it would be fine to just look at the last finalised head, and run the pre-checks as usual since the node_url is specifically either a collator, or relay chain node. 🤔 There are two commits on the associated PR which adds some more context.

from polkadot-stps.