RFR: 1635: Add configurable regex message filter to BotLogstashHandler

[Erik Joelsson]

For increased flexibility with how certain log messages are handled, I need to be able to apply custom regex replacements on log messages going to logstash. This patch adds such a configurable option.

-------------

Commit messages:
 - Can be final
 - First stab

Changes: https://git.openjdk.org/skara/pull/1397/files
 Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1397&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-1635
  Stats: 28 lines in 2 files changed: 27 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/skara/pull/1397.diff
  Fetch: git fetch https://git.openjdk.org/skara pull/1397/head:pull/1397

PR: https://git.openjdk.org/skara/pull/1397