Optimise fromEnriched function

[chuwy]

snowplow-s3-loader/src/main/scala/com/snowplowanalytics/s3/loader/processing/Batch.scala

Lines 36 to 40 in 564d12d

	def fromEnriched(inputs: List[Result]): Batch[List[Result]] = {
	val earliest = Common.getEarliestTstamp(inputs)
	val count = inputs.length
	Batch(Meta(earliest, count), inputs)
	}

Currently it does multiple linked list traversals that can be reduced into one:

1. flatMap traversal to get all timestamps
2. Sorting which is even worse than plain traversal
3. Length-calculation which can be fused into main traversal

We can have a single fold instead of above three.