[skara] RFR: 572: Auto-correct PR title if it is a prefix of the JBS issue title

[Magnus Ihse Bursie]

The PR bot should auto-correct PR titles if they are a known prefix of a JBS issue title instead of showing a warning that there is a mismatch between PR and JBS title.

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Commit messages:
 - Also update PR body to remove the "...end of title" part.
 - Initial implementation of handling cut-off titles.
 - Create test for cut-off titles in Github

Changes: https://git.openjdk.java.net/skara/pull/1023/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1023&range=00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-572
  Stats: 107 lines in 2 files changed: 94 ins; 7 del; 6 mod
  Patch: https://git.openjdk.java.net/skara/pull/1023.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1023/head:pull/1023

PR: https://git.openjdk.java.net/skara/pull/1023