RFR: 1575: Adjust the pull request APIs in HostedRepository [v2]

[Guoxiong Li]

> Hi all,
> 
> This patch mainly has the following changes in `HostedRepository` and its sub-classes. And the usages of the changed methods are also changed.
> 
> 1. Change the name of the `pullRequests(ZonedDateTime updatedAfter)` to `pullRequestsAfter` so that it is consistent as the `openPullRequestsAfter`.
> 2. Add the new api `openPullRequests` to get all the open pull requests.
> 3. Change the implementation of the method `pullRequests()` to get all the pull requests (included open and closed)
> 
> Thanks for taking the time to review.
> 
> Best Regards,
> -- Guoxiong

Guoxiong Li has updated the pull request incrementally with one additional commit since the last revision:

  Add parameter about max pages and order.

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Changes:
  - all: https://git.openjdk.org/skara/pull/1367/files
  - new: https://git.openjdk.org/skara/pull/1367/files/2a9e48fa..45aa7ab8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=skara&pr=1367&range=01
 - incr: https://webrevs.openjdk.org/?repo=skara&pr=1367&range=00-01

  Stats: 10 lines in 2 files changed: 6 ins; 4 del; 0 mod
  Patch: https://git.openjdk.org/skara/pull/1367.diff
  Fetch: git fetch https://git.openjdk.org/skara pull/1367/head:pull/1367

PR: https://git.openjdk.org/skara/pull/1367