[jdk13u-dev] RFR: 8250928: JFR: Improve hash algorithm for stack traces

[Ekaterina Vergizova]

I would like to backport 8250928 to 13u, it's already included into 11u.

The patch applies almost cleanly except for the second hunk of jfrStackTrace.cpp due to different context (8236743 is not in 13u), reapplied manually.

Tested with tier1 and jdk/jfr.

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Commit messages:
 - Backport 12879e91b43798750f9c7656dacc5085dd20cc96

Changes: https://git.openjdk.java.net/jdk13u-dev/pull/12/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk13u-dev&pr=12&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8250928
  Stats: 4 lines in 1 file changed: 2 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk13u-dev/pull/12.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk13u-dev pull/12/head:pull/12

PR: https://git.openjdk.java.net/jdk13u-dev/pull/12