Add PR number to the release notes entry in a new PR

[steveburnett]

Automatically add the number of the pull request to the release note entry example in the pull request.

Expected Behavior or Use Case

When a pull request is created, replace 12345 in https://github.com/prestodb/presto/blob/master/pull_request_template.md with the number of the newly generated pull request. See the screenshot in Example Screenshots.

Presto Component, Service, or Connector

The pull request generation process.

Possible Implementation

?

Example Screenshots (if appropriate):

When a PR is generated, the PR generation process should replace 12345 in this screenshot with the number of the new PR.

Context

Including the PR number in a release note entry in the Presto Release Notes is valuable to help readers of the release notes quickly find the PR a release note entry is sourced from. For an example, see the notes for Release 0.286.

Manually editing the individual release note entries during the release notes process to include the PR that the entry is sourced from takes significant work and time, and can lead to errors.

#22665 addressed this by asking the creator of each PR to manually add the new PR number in the release note entry for their PR, and by improving the PR template with a placeholder formatted value for the release note to help the PR creator correctly format the PR number in their release note entry.

@rschlussel suggested this process could be improved if the new PR number could automatically be added to the new PR's release note entry example, and I offered to write the idea up in an issue.