RFR: 7903659 Verify Problemlist contents

[Ludvig Janiuk]

I think it would be a good idea to verify those...

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Commit messages:
 - fixup
 - minor
 - ws
 - check duplicates
 - more details on formats
 - more coverage
 - start on actual tests
 - Merge remote-tracking branch 'upstream/master' into verify-problemlists
 - better output
 - start on explicit checks
 - ... and 4 more: https://git.openjdk.org/jtreg/compare/4b2cb31f...60f1f777

Changes: https://git.openjdk.org/jtreg/pull/181/files
 Webrev: https://webrevs.openjdk.org/?repo=jtreg&pr=181&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903659
  Stats: 325 lines in 14 files changed: 324 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jtreg/pull/181.diff
  Fetch: git fetch https://git.openjdk.org/jtreg.git pull/181/head:pull/181

PR: https://git.openjdk.org/jtreg/pull/181