remove nLastResend because it's unnecessary now that rebroadcasts always happen at least 12 hours later

- expose info about number of txns in unbroadcast set and whether a mempool entry's tx has passed initial broadcast
- makes rpcs more informative and allows for more explicit testing, eg tracking if tx is in unbroadcast set
before and after originating node connects to peers (adds this in mempool_unbroadcast.py)
- adds mempool method InUnbroadcast to quickly query for tx inclusion in  mempool's unbroadcast set

- before reattempting broadcast for unbroadcast txns, check they are in mempool and remove if not
- this protects from memory leaks and network spam just in case unbroadcast set (incorrectly) has extra txns
- check that tx is in mempool before adding to unbroadcast set to try to prevent this from happening

… entries

- mempool entry 'unbroadcast' field changes when initial broadcast is complete,
so anytime you want to compare mempool entries, wait for initial broadcast to complete
('unbroadcast' = False) otherwise it may change in between calls
- mempool_packages.py needs to do this especially because it compares entries as a whole
and compares getrawmempool with getmempoolentry

- exposes info about number of txns in unbroadcast set and whether a mempool entry's tx has passed initial broadcast
- makes rpcs more informative and allows for more explicit testing, eg tracking if tx is in unbroadcast set
before and after originating node connects to peers (adds this in mempool_unbroadcast.py)
- adds mempool method InUnbroadcast to quickly query for tx inclusion in  mempool's unbroadcast set

- before reattempting broadcast for unbroadcast txns, check they are in mempool and remove if not
- this protects from memory leaks and network spam just in case unbroadcast set (incorrectly) has extra txns
- check that tx is in mempool before adding to unbroadcast set to try to prevent this from happening

… entries

- mempool entry 'unbroadcast' field changes when initial broadcast is complete,
so anytime you want to compare mempool entries, wait for initial broadcast to complete
('unbroadcast' = False) otherwise it may change in between calls
- mempool_packages.py needs to do this especially because it compares entries as a whole
and compares getrawmempool with getmempoolentry