Add support for pushing read-only transactions

[yogevmas]

Leap v4 added "Parallelized speculative read-only transaction execution" (See https://eosnetwork.com/blog/antelope-leap-4-released/). read-only is an option of push-transaction (See https://docs.eosnetwork.com/manuals/leap/latest/cleos/command-reference/push/push-transaction/)