[Rev 03] RFR: 6674: Optimize finding of first start time and first & last end times

[Henrik Dafgård]

> This optimization relies on the fact that event lanes are sorted by timestamp. This allows us to skip performing very costly comparisons when finding the first start time or first/last end times of an IItemCollection and instead just get the first or last events in each lane and find the event in that set that was earliest or last, respectively.
> 
> This PR also removes the associated aggregators to strongly encourage downstream users to make use of the added RulesToolkit methods.

The pull request has been updated with 1 additional commit.

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Added commits:
 - f102abbb: Add test case with custm jfr file

Changes:
  - all: https://git.openjdk.java.net/jmc/pull/31/files
  - new: https://git.openjdk.java.net/jmc/pull/31/files/9fdd627c..f102abbb

Webrevs:
 - full: https://webrevs.openjdk.java.net/jmc/31/webrev.03
 - incr: https://webrevs.openjdk.java.net/jmc/31/webrev.02-03

  Stats: 89 lines in 5 files changed: 86 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jmc/pull/31.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/31/head:pull/31

PR: https://git.openjdk.java.net/jmc/pull/31