Do not iterate elements in bounded queue/channel's destructor when needs_drop returns false

[taiki-e]

https://doc.rust-lang.org/std/mem/fn.needs_drop.html

Note that drop_in_place already performs this check, so if your workload can be reduced to some small number of drop_in_place calls, using this is unnecessary. In particular note that you can drop_in_place a slice, and that will do a single needs_drop check for all the values.

Types like Vec therefore just drop_in_place(&mut self[..]) without using needs_drop explicitly. Types like HashMap, on the other hand, have to drop values one at a time and should use this API.