Add a `assertSegmentDuration` function in custom assertions

[amychisholm03]

Description

As we migrate over our instrumentation to use the tracing channel, we need an easy and standard way to assert segment durations. So far different test suites do it a bit differently, but the closest one that could be used across packages is assertSegmentState in the memcached versioned tests:

node-newrelic/test/versioned/memcached/memcached.test.js

Lines 1034 to 1050 in 915b320

	/**
	* Asserts that the current segment has the expected name, has ended,
	* and has a duration within a reasonable threshold of the actual measured time.
	* @param {TraceSegment} segment segment to check
	* @param {string} expectedName expected segment name
	* @param {Array} actualTime process.hrtime() duration of the actual call
	*/
	function assertSegmentState(segment, expectedName, actualTime) {
	assert.equal(segment.name, expectedName)
	assert.equal(segment._isEnded(), true, 'segment should have ended')
	const segmentDuration = segment.getDurationInMillis()
	const actualDuration = hrToMillis(actualTime)
	assert.ok(
	Math.abs(segmentDuration - actualDuration) < 1,
	`segment duration (${segmentDuration}ms) should be within 1ms of actual duration (${actualDuration}ms)`
	)
	}

.

We need to create this function in custom-assertions and implement it across our test suites. Instead of a strict 1ms (or similar constant) threshold, we should use a percentage threshold.

Acceptance Criteria

• all test suites that test segment durations (excluding ones where you can explicitly test duration like sleep(2) in mysql2) use this new function and they still pass

[Newrelic-Boomi]

https://new-relic.atlassian.net/browse/NR-539787