Avoid magic numbers in the Config

[yellowhatter]

Describe the feature

There are magic numbers in our Config, like -1 for various timeouts:

zenoh/commons/zenoh-config/src/lib.rs

Line 447 in 075f2ad

wait_before_drop: i64,

zenoh/io/zenoh-transport/src/manager.rs

Line 44 in 075f2ad

fn duration_from_i64us(us: i64) -> Duration {

That is an awful, implicit, and non-documented way of configuring infinite duration (@Mallets )

This issue is about reviewing and removing magic numbers from the config.