RFR: 2037: Change the order of bots in PullRequestBotFactory

[Zhao Song]

Today, when restarting the bot, I found that the IssueBot was down for a long time(about 30 minutes), and then I realized that in PullRequestBotFactory, we created all pullRequestBots first, then CSRIssueBots, and IssueBots last. 

After the bot is restarted, the botRunner would run all pullRequestBots first and we have a lot of pullRequestBots, so it will take a lot of time. And if users make changes to issues in JBS during this interval, the IssueBot may not be able to get all updated issues. It's really bad. 

To solve this problem, we could to reverse the order of bots in PullRequestBotFactory, therefore we could make sure IssueBot will be run firstly.

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

Commit messages:
 - override replaces
 - SKARA-2037

Changes: https://git.openjdk.org/skara/pull/1558/files
 Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1558&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-2037
  Stats: 14 lines in 2 files changed: 14 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/skara/pull/1558.diff
  Fetch: git fetch https://git.openjdk.org/skara.git pull/1558/head:pull/1558

PR: https://git.openjdk.org/skara/pull/1558