OOPify the `PollingSystem` encoding

[armanbilge]

Well, Daniel wants us to anyway 😝 for some reason I'm not crazy about this idea, but I won't die on this hill.

Basically, we should make an abstract class Poller or something, and move these methods onto that.

cats-effect/core/jvm-native/src/main/scala/cats/effect/unsafe/PollingSystem.scala

Lines 38 to 56 in 58f695f

	def closePoller(poller: Poller): Unit
	/**
	* @param nanos
	* the maximum duration for which to block, where `nanos == -1` indicates to block
	* indefinitely.
	*
	* @return
	* whether any events were polled
	*/
	def poll(poller: Poller, nanos: Long, reportFailure: Throwable => Unit): Boolean
	/**
	* @return
	* whether poll should be called again (i.e., there are more events to be polled)
	*/
	def needsPoll(poller: Poller): Boolean
	def interrupt(targetThread: Thread, targetPoller: Poller): Unit

Follow-up to:

• Polling system #3332

[djspiewak]

Wontfix