RFR: 1594: Convert rest of bots polling PRs and Issues to use new pollers

[Erik Joelsson]

The new PullRequestPoller has now been in use in the PullRequestBot for a while, and hopefully most of the kinks have been ironed out. I think it's time to convert the rest of the bots that poll PRs (and the CSRIssueBot that polls Issues) to use the new pollers. 

The conversion is pretty straight forward. In the case of the CSRBots, they were missing the retry callback, so I added that functionality in line with other bots.

The new factory tests needed to be modified slightly, as the PullRequestPoller calls to the Forge/Host object of a repository during initialization, so we need a TestHost instance there instead of `null`.

I deliberately left out two bots here, the JEPBot and the TestInfoBot. The TestInfoBot is handled separately already in #1411. For the JEPBot, I think it needs a general overhaul. In the end it should function more or less the same as the CSRBot, but I'm still not sure that the CSRBot is where I want it to be.

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Commit messages:
 - Fix tests
 - SKARA-1594

Changes: https://git.openjdk.org/skara/pull/1412/files
 Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1412&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-1594
  Stats: 186 lines in 9 files changed: 41 ins; 104 del; 41 mod
  Patch: https://git.openjdk.org/skara/pull/1412.diff
  Fetch: git fetch https://git.openjdk.org/skara pull/1412/head:pull/1412

PR: https://git.openjdk.org/skara/pull/1412