Code review changes.

…nd(...) (java-native-access#11)

Motivation:

We need to carefully handle the scheduling of timeouts and calling of quiche_conn_send to follow the pattern outlined by quiche:

* https://docs.rs/quiche/0.6.0/quiche/struct.Connection.html#method.send
* https://docs.rs/quiche/0.6.0/quiche/#generating-outgoing-packets

Modifications:

- Rename methods to make it easier to understand the code
- Schedule timeouts at the correct time
- Call quiche_conn_send on the correct time
- Add some comments to make it easier to understand the code and the state-machine.

Result:

Correctly use quiche API