* refactor: add a Mediator class to decouple tr_session and tr_port_forwarding
* refactor: add tr_port_forwarding::Mediator::privatePeerPort()
* refactor: add tr_port_forwarding::Mediator::onPortForwarded()
* chore: avoid unnecessary include of timer.h in other headers
* refactor: use a uniform timerMaker() API in mediators
* refactor: make tr_peerIoSetEnabled() a member method
* refactor: make tr_peerIoFlushOutgoingProtocolMsgs() a member method
* refactor: make tr_peerIoFlush() a member method
* refactor: make tr_peerWriteBytes() a member method
* refactor: make tr_peerWriteBuf() a member method
* refactor: make tr_peerIoGetWriteBufferSpace() a member method
* chore: remove unused declaration
* refactor: make tr_peerIoUtpInit() a member method
* refactor: make tr_peerIoNew() a member method
* refactor: make tr_peerIoNewOutgoing() a member method
* refactor: make tr_peerIoNewIncoming() a member method
A Cœur