Change streams track the timestamp of every seen oplog entry inside the `CollectionScan::setLatestOplogEntryTimestamp(const Record& record)` function.
This function previously BSONified the oplog entry only to extract the 'ts' field again.
For oplog records, the timestamp is directly encoded in the record id, so this conversion can be saved.

This change adds a fast path inside `setLatestOplogEntryTimestamp()` for extracting the numeric timestamp value from the record id, skipping the unnecessary BSONificiation.
This makes the `setLatestOplogEntryTimestamp()` function run ~55% faster in optimized builds. This is beneficial because the function is called for every oplog entry encountered by a change stream, not just the oplog entries that make it through the change stream's oplog match filter.