When running under Java 11, `Instant.now()` has mi...

# strikt

[Eric]

When running under Java 11, Instant.now() has microseconds, but under Java 8, only millis. So sometimes running tests inside a Java 11 container using isEqualTo will fail that passed under Java 8.

I just added this to our extensions:

// Java 11 Instant.now() has more resolution than Java 8, so need to only compare millis, not micros+
public fun DescribeableBuilder<Instant>.isApproximatelyEqualTo(value: Instant, delta: Duration = Duration.ofMillis(1)) {
    get { Duration.between(this, value).abs() }.isLessThan(delta)
}

Not sure if this is worth a PR or if it would go in core or jvm module.