chore: create admin-only issue form, improve and add discussion forms

[HonkingGoose]

Changes

• Create administrator-only Issue form
• Drop all other Issue forms
• Small style fixes for the comments from our label action action/bot
• Small update to our triage guide, users with triage access can also apply/dismiss labels on Discussions
• Convert content from old issue forms to new discussion forms
• Rename existing discussion forms

Context

Seeing as we don't want users to create an issue anyway, we can simplify the form for the maintainers convenience.

I'm also improving our Discussion Forms, to replace the old Issue Forms.

Documentation (please check one with an [x])

• I have updated the documentation, or
• No documentation update is required

How I've tested my work (please select one)

I have verified these changes via:

• Code inspection only, or
• Newly added/modified unit tests, or
• No unit tests but ran on a real repository, or
• Both unit tests + ran on a real repository

[HonkingGoose]

I'm ready for another round of review.

[renovate-release]

🎉 This PR is included in version 35.105.1 🎉

The release is available on:

• GitHub release
• 35.105.1

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