Add additional options to PR template and clarify some

[mbg]

Extends the PR template with some new options and clarifies some existing ones.

Risk assessment

For internal use only. Please select the risk level of this change:

• Low risk: Changes are fully under feature flags, or have been fully tested and validated in pre-production environments and are highly observable, or are documentation or test only.

Which use cases does this change impact?

N/A.

How did/will you validate this change?

• None - I am not validating these changes.

If something goes wrong after this change is released, what are the mitigation and rollback strategies?

• Rollback - Change can only be disabled by rolling back the release or releasing a new version with a fix.

How will you know if something goes wrong after this change is released?

N/A

Merge / deployment checklist

• Confirm this change is backwards compatible with existing workflows.
• Consider adding a changelog entry for this change.
• Confirm the readme and docs have been updated if necessary.

[Copilot]

Pull Request Overview

This PR enhances the pull request template by reorganizing the "Which use cases does this change impact?" section into clearer categories and adding a new section for special merge considerations.

Key Changes

• Restructured use case options into three distinct categories: Workflow types, Products, and Environments, replacing the previous flat list
• Added a new section "Are there any special considerations for merging or releasing this change?" to help identify dependencies or preconditions before merging
• Clarified the instruction comment to guide users on when to retain options if unsure