RFR: 1594: Convert rest of bots polling PRs and Issues to use new pollers [v2]

[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.

Erik Joelsson has updated the pull request incrementally with one additional commit since the last revision:

  Added more comments describing limitations with the poller

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Changes:
  - all: https://git.openjdk.org/skara/pull/1412/files
  - new: https://git.openjdk.org/skara/pull/1412/files/ead5f3ce..db231a8a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=skara&pr=1412&range=01
 - incr: https://webrevs.openjdk.org/?repo=skara&pr=1412&range=00-01

  Stats: 18 lines in 1 file changed: 10 ins; 0 del; 8 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