Adopt new GitHub Issues Forms syntax

[ethan-kusters]

GitHub has support for a new Forms-style of GitHub Issues that seems like a significant improvement over the default markdown templating system: https://github.blog/changelog/2021-06-23-issues-forms-beta-for-public-repositories/.

There's some documentation on the syntax here: https://docs.github.com/en/communities/using-templates-to-encourage-useful-issues-and-pull-requests/syntax-for-issue-forms.

We should migrate our existing templates over to the new format to make it easier for contributors to file bug reports and feature requests.