RFR: 1626: 8-pool records not consumed by openjdk8uX fixversions

[Erik Joelsson]

The logic for matching *-pool records in backports is not matching openjdk8uX to an issue with fixVersion 8-pool. The version parsing logic for OpenJDK releases is a bit of a minefield, where sometimes the prefix is relevant and sometimes not. This fix isolates ignoring of the prefix to just matching of *-pool records in Backports.java. I'm reusing the same regex that already existed for doing something similar in that class. The previous usage was in the logic for the hgupdate-sync label.

I don't think this will introduce any unwanted behavior, but I would appreciate if someone else could help think it through.

I chose to prioritize exact *-pool matches and fallback to matching just the numeric part of the feature version as a fallback. This means that if we decided to add openjdk8-pool as a pool version in the future, that would continue to work.

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Commit messages:
 - SKARA-1626

Changes: https://git.openjdk.org/skara/pull/1389/files
 Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1389&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-1626
  Stats: 28 lines in 2 files changed: 23 ins; 2 del; 3 mod
  Patch: https://git.openjdk.org/skara/pull/1389.diff
  Fetch: git fetch https://git.openjdk.org/skara pull/1389/head:pull/1389

PR: https://git.openjdk.org/skara/pull/1389