RFR: 6831: Add chunk ranges to IItemCollection

[Henrik Dafgård]

This PR adds the timeranges for all chunks that make up an IItemCollection, thus allowing downstream consumers, rules
and the JMC UI (with plugins) to make accurate inferences with regards to the timespans when events could possibly have
been emitted.

-------------

Commit messages:
 - Add chunk ranges to IItemCollection

Changes: https://git.openjdk.java.net/jmc/pull/81/files
 Webrev: https://webrevs.openjdk.java.net/jmc/81/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JMC-6831
  Stats: 163 lines in 16 files changed: 124 ins; 0 del; 39 mod
  Patch: https://git.openjdk.java.net/jmc/pull/81.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/81/head:pull/81

PR: https://git.openjdk.java.net/jmc/pull/81