[lworld] RFR: 8376752: [lworld] clarify/organize Valhalla ProblemLists

[Daniel D. Daugherty]

A trivial fix to clarify/organize Valhalla ProblemLists.

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Commit messages:
 - Merge branch 'lworld' into JDK-8376752
 - 8376752: [lworld] clarify/organize Valhalla ProblemLists

Changes: https://git.openjdk.org/valhalla/pull/2007/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=2007&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8376752
  Stats: 537 lines in 25 files changed: 425 ins; 91 del; 21 mod
  Patch: https://git.openjdk.org/valhalla/pull/2007.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/2007/head:pull/2007

PR: https://git.openjdk.org/valhalla/pull/2007