RFR: 8286925: Move JSON parser used in JFR tests to test library

[Erik Gahlin]

Could I have a review of a change that moves the JSON parser used in JFR tests to the test library so it can be used by other tests.

Testing: test/jdk/jdk/jfr/tool

Thanks
Erik Gahlin

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Commit messages:
 - Initial

Changes: https://git.openjdk.java.net/jdk/pull/8763/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8763&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8286925
  Stats: 4 lines in 2 files changed: 1 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8763.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8763/head:pull/8763

PR: https://git.openjdk.java.net/jdk/pull/8763