RFR: 7349: JFR Parser struct types hashcode is not stable

[Jaroslav Bachorik]

7349: JFR Parser struct types hashcode is not stable

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Commit messages:
 - JMC-7349: JFR Parser struct types hashcode is not stable

Changes: https://git.openjdk.java.net/jmc/pull/287/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmc&pr=287&range=00
  Issue: https://bugs.openjdk.java.net/browse/JMC-7349
  Stats: 26 lines in 1 file changed: 25 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jmc/pull/287.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/287/head:pull/287

PR: https://git.openjdk.java.net/jmc/pull/287