Consider renaming `UsePreviousTimeOnInvalidTimestamp` timestamp extractor

Kafka Streams ships couple of different timestamp extractors, one named `UsePreviousTimeOnInvalidTimestamp`.

Given the latest improvements with regard to time tracking, it seems appropriate to rename this class to `UsePartitionTimeOnInvalidTimestamp`, as we know have fixed definition of partition time, and also pass in partition time into the `#extract(...)` method, instead of some non-well-defined "previous timestamp".

KIP-530: https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=130028807