Add TCP, TCPDNS and TLSDNS write timer
When the outgoing TCP write buffers are full because the other party is not reading the data, the uv_write() could wait indefinitely on the uv_loop and never calling the callback. Add a new write timer that uses the tcp-idle-timeout
value to interrupt the TCP connection when we are not able to send data for defined period of time.
Closes #3132 (closed)
Edited by Ondřej Surý