This removes some of the last mentions of the AppVeyor name. Don't change the title, we don't want the word to appear in the CLs
Also problem: the last references are in the changelogs but I don't want to modify them without committee approval.
## PR Context
it was removed, #8686
- Update contribution guidelines to make updating the changelog required
- add a checklist to PR template
Comment by @SteveL-MSFT :
> Everyone should understand that we are always open to feedback and nothing is set in stone. Based on a team discussion, one of the biggest costs for a release is creating the ChangeLog hence updating this document to push it to the contributor most aware of why the changes are being made and ideally how it's useful to end users.
* Update coding guidelines to make it more concrete and useful in a review process.
* Add a section about security
* Address comments
* Update .spelling
* Address more comments
* Address comment about the security section
* Fix 'i.e.' and 'e.g.'
* Update .spelling
* One more tweak
* Add motivation for using 'nameof'
