chore(github): Suspend GitHub Discussions Ideas and revert to feature request issues

[Savio-Sou]

Description

Problem*

The move towards using GitHub Discussions to suggest ideas was found premature following #2672, as it introduced additional frictions in:

• Requiring the need to switch between Issues / Discussions to distill ideas raised
• Discussions are not manageable on GitHub's Project Board

Summary*

Until we can formally define how the Ideas section in GitHub Discussions should be used, this PR reverts the repo back to using GitHub Issues for feature requests for us to move faster in the meantime.

Documentation*

Check one:

• No documentation needed.
• Documentation included in this PR.
• [Exceptional Case] Documentation to be submitted in a separate PR.

PR Checklist*

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.

[jfecher]

LGTM.

I'll leave this for others to approve though.

[jfecher]

Would the new "feature request" issue type still cover internal-only features or refactorings such as: #4151 ? If not, we'd need another category for them.

[Savio-Sou]

Would the new "feature request" issue type still cover internal-only features or refactorings

Yes.

Unless there is a need to distinguish internal vs external, which I personally don't see at the moment.