Add a "office use only" style section to Pull Request templates

### Checklist

- [X] I have verified this is the correct repository for opening this issue.
- [X] I have verified no other issues exist related to my request.

### Is Your Feature Request Related To A Problem? Please describe.

When we are accepting pull requests, there are a number of checks that we would like to keep in our minds to ensure we're not making more work for ourselves in the future. It would be good to add these to the PR template so that we can ensure they are done.

### Describe The Solution. Why is it needed?

Notice on many forms there are sections labeled "For Office Use Only". The purpose of these sections is for the company to ensure that they complete various processes. Likewise adding this section to the PRs is a reminder for Chocolatey maintainers to ensure various things are covered off.

Some examples:

- Does this PR affect other Chocolatey products that may need a corresponding change?
- For example: Chocolatey Licensed Extension, Chocolatey GUI, Chocolatey Agent, Boxstarter(?), etc.
- Is the PR attached to an Issue that's been attached to a milestone?
- Do any of these changes need to be made to other branches?
- For example: Updates to just the Pester tests likely need to be pulled into the `master` branch so that hotfixes are getting the full suite of tests.

### Additional Context

This came up during discussion at the Engineering Team Meeting December 21, 2023 (not recorded, nor were minutes taken, was more of a standup than a regular meeting).

### Related Issues

_No response_