* Unify autoIS/send_smth functions
* Rename autoix-mempool.py -> autois-mempool.py
* Make sure create_raw_trx produces expected results
* Make sure sender has enough inputs and nodes are synced before starting the actual test
* Mine one block to clean mempool up
* 2 blocks is enough for IS on regtest
This also unifies it across different IS tests
* Allow wait_for_instantlock to be called on any node, not only on the one that has the tx in the wallet
* No need to query for tx this often in wait_for_instantlock
* Rename create_raw_trx -> create_raw_tx
* Fund sender with a single TX instead of 30
