Revisit the merging of HoodieDefaultTimeline

Revisit the logic below to see if there is inefficiency.  This is used by HoodieSyncClient.
{code:java}
public HoodieDefaultTimeline mergeTimeline(HoodieDefaultTimeline timeline) {
Stream instantStream = Stream.concat(instants.stream(), timeline.getInstants()).sorted();
Function> details = instant -> {
if (instants.stream().anyMatch(i -> i.equals(instant))) {
return this.getInstantDetails(instant);
} else {
return timeline.getInstantDetails(instant);
}
};
return new HoodieDefaultTimeline(instantStream, details);
} {code}

## JIRA info

- Link: https://issues.apache.org/jira/browse/HUDI-5481
- Type: Improvement

Start with HoodieDefaultTimeline.mergeTimeline and its use by HoodieSyncClient. Examine the stream merging, sorting, and instant-detail lookup shown in the issue, then determine whether the current logic is inefficient. Done means the inefficiency question is answered and any resulting change is validated for HoodieSyncClient.

Written by the indexing model from the issue text.