[jdk11u-dev] RFR: 8206085: Refactor langtools/tools/javac/versions/Versions.java

[Christoph Langer]

Backport of JDK-8206085. Needs some resolving to remove parts that can only work with JDK12.

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Commit messages:
 - Backport 28e2dea71d24962aeb3a26166dbb55ebe8f30ca6

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/314/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=314&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8206085
  Stats: 144 lines in 1 file changed: 72 ins; 10 del; 62 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/314.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/314/head:pull/314

PR: https://git.openjdk.java.net/jdk11u-dev/pull/314