RFR: SKARA-971: Stop clumping up logs in logstash [v5]

[Erik Joelsson]

> I would like to change how we send logs to logstash so each log message is stored as an individual document. To make this more practical, we need to add some more meta data to each message so we can properly filter them. I suggest adding the following:
> 
> instance_start_time: An ISO_INSTANT time stamp string indicating when this JVM instance was started.
> work_id: A running counter generated ID for each work item, rest request or periodic check, which was previously clumped up in one log message.
> work_item: For work items, store the item toString()

Erik Joelsson has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains seven additional commits since the last revision:

 - Use HttpClient.sendAsync directly to send to logstash
 - Merge branch 'master' into SKARA-971-logstash
 - Fix start time stamp
 - Added simple test of LogContext
 - Update bots/cli/src/main/java/org/openjdk/skara/bots/cli/BotLogstashHandler.java
   
   Co-authored-by: Robin Westberg <robin at westberg.se>
 - Corrected comment
 - Implemented LogContext

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

Changes:
  - all: https://git.openjdk.java.net/skara/pull/1120/files
  - new: https://git.openjdk.java.net/skara/pull/1120/files/6566eb8a..2c315bc2

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=skara&pr=1120&range=04
 - incr: https://webrevs.openjdk.java.net/?repo=skara&pr=1120&range=03-04

  Stats: 433 lines in 22 files changed: 354 ins; 9 del; 70 mod
  Patch: https://git.openjdk.java.net/skara/pull/1120.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1120/head:pull/1120

PR: https://git.openjdk.java.net/skara/pull/1120