[grid] Fix flaky event bus tests by dedicated threading, reverting the polling loop logic and increasing poll timeout - #9383

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Description

Event bus tests when run using the following command would fail :
bazel test --cache_test_results=no --runs_per_test=20 //java/server/test/org/openqa/selenium/events:EventBusTest --test_filter=org.openqa.selenium.events.EventBusTest#

Motivation and Context

The pattern observed in the failure was that the countdown latch would keep waiting and never receive the messages as expected intermittently event after increasing the wait times.
This was primarily due to errors :

1. ClosedSelectorException

java.nio.channels.ClosedSelectorException
	at java.base/sun.nio.ch.SelectorImpl.ensureOpen(SelectorImpl.java:75)
	at java.base/sun.nio.ch.SelectorImpl.keys(SelectorImpl.java:80)
	at zmq.ZMQ.poll(ZMQ.java:647)
	at org.zeromq.ZMQ$Poller.poll(ZMQ.java:3892)

2. CancelledKeyException

java.nio.channels.CancelledKeyException
	at java.base/sun.nio.ch.SelectionKeyImpl.ensureValid(SelectionKeyImpl.java:71)
	at java.base/sun.nio.ch.SelectionKeyImpl.interestOps(SelectionKeyImpl.java:90)
	at zmq.ZMQ.poll(ZMQ.java:663)
	at org.zeromq.ZMQ$Poller.poll(ZMQ.java:3892)

This was observed when tcp transport layer was used in creating the socket when the poll wait time was set to return immediately i.e. set to 0. Once this was updated to a higher value, the tests were not longer flaky but the run time was very slow since a scheduled thread ran and waited for a bit in each run.
Reverting the polling loop to

Additionally, closed the poller during resource clean up. Added a separate dedicated thread to publish messages.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• I have read the contributing document.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.