Expand scope of duplicate pr checker for release pull request

[nerrad]

Fixes: #31

Prior to the changes in this pr, the release pull request automation checked for open pull requests that matched the title of the release pull request. However, this meant that whenever we re-opened a release branch for patch releases, a new pr would be created for that branch even though we're only reopening it to create a patch branch based off of it.

So, this pr updates the duplicate checker for the release pull request automation so that:

• it includes closed prs in the search.
• a duplicate is only triggered if the title matches and pr is not merged.

This allows us to still close an unmerged release pull request if created by accident or needing to fix the generated template/changelog.

[github-actions]

➿ Code coverage

Filename	Statements	Branches	Functions	Lines
lib/automations/todos/utils/get-todos.js	100%	100%	100%	100%
lib/automations/todos/utils/get-diff.js	100%	100%	100%	100%
lib/automations/todos/utils/parse-to-do.js	100%	97.67%	100%	100%
lib/automations/todos/utils/get-details.js	100%	90.91%	100%	100%
lib/debug.js	66.67%	50%	100%	66.67%
lib/automations/todos/utils/check-for-duplicate-issue.js	100%	100%	100%	100%
lib/automations/todos/index.js	100%	100%	100%	100%
lib/automations/todos/runner.js	88.89%	66.67%	100%	88.89%
lib/automations/todos/pull-request-handler.js	90.48%	83.33%	100%	90.48%
lib/automations/todos/templates/index.js	100%	100%	100%	100%
lib/automations/todos/templates/comment.js	100%	100%	100%	100%
lib/automations/todos/templates/issue.js	100%	100%	100%	100%
lib/automations/todos/templates/issue-from-merge.js	100%	100%	100%	100%
lib/automations/todos/templates/title-change.js	100%	100%	100%	100%
lib/automations/todos/templates/reopen-closed.js	100%	100%	100%	100%
lib/utils/index.js	100%	100%	100%	100%
lib/utils/milestones.js	85.19%	60%	100%	85.19%
lib/utils/helpers.js	85.71%	66.67%	100%	83.33%
lib/automations/todos/pull-request-merge-handler.js	91.3%	87.5%	100%	91.3%
lib/automations/todos/utils/reopen-closed.js	100%	100%	100%	100%
lib/automations/todos/push-handler.js	92%	90%	100%	92%
lib/automations/todos/issue-rename-handler.js	100%	100%	100%	100%
lib/automations/release/config/validate-config.js	92.59%	95%	100%	92.59%
lib/automations/release/index.js	100%	100%	100%	100%
lib/automations/release/runner.js	87.5%	50%	100%	87.5%
lib/automations/release/branch-create-handler.js	89.66%	80%	66.67%	91.23%
lib/automations/release/templates/index.js	83.33%	40%	75%	83.33%
lib/automations/release/utils/index.js	100%	100%	100%	100%
lib/automations/release/utils/get-release-version.js	90.91%	87.5%	100%	90.91%
lib/automations/release/utils/is-patch-release.js	100%	100%	100%	100%
lib/automations/release/utils/get-release-branch.js	62.5%	55.56%	100%	62.5%
lib/automations/release/utils/duplicate-pr-checker.js	100%	100%	100%	100%
lib/automations/release/utils/has-milestone.js	100%	100%	100%	100%
lib/utils/changelog/index.js	100%	100%	100%	100%
lib/utils/changelog/common/changelog.js	83.96%	56.1%	86.49%	83%
lib/automations/release/config/index.js	75%	0%	100%	75%
lib/automations.js	0%	100%	100%	0%
lib/if-not-fork.js	0%	0%	0%	0%
lib/utils/version.js	0%	0%	0%	0%
lib/typedefs.js	0%	100%	100%	0%
lib/index.js	0%	0%	0%	0%