Updates handle_reorg to work with the current version of the Responder (the old code was outdated and broken).
`check_tx_in_chain` was only used by `handle_reorgs`, and made not much sense at this point. The method need to check if the transaction is in mempool or blockchain, so it seems to make more sense bulding on top of `get_transaction`.
- Adds a PRG based on a hardcoded seed to make the tests reproducible (get_random_value_hex)
- Updates all the tests replacing urandom for get_random_value_hex
- Properly places misplaced bitcoin_cli in bitcoin_sim_tests
- Typos
bitcoin_cli as a global variable in the main __init__.py was creating issues related to http.client.CannotSendRequest: Request-sent and connection re-usage. Define a new connection per request.
The modules that need to run either bitcoind or the api do now reference to the fixture in the first test that needs it. Since the fixtures are definexd session-wise the rest of the modules will have access to them from that point on.
