docs: add verified adapters section (#91849)
## Summary
- Introduces the **verified adapter** concept to deployment docs: open
source adapters that run the Next.js compatibility test suite, hosted
under the Next.js GitHub org
- Splits the adapter list on the deploying page into **Verified
Adapters** (Vercel, Bun) and **Other Platforms** (unverified
integrations)
- Documents the Next.js team's commitments for verified adapters and
Ecosystem Working Group participants (coordinated testing, early access,
direct support)
- Notes that Cloudflare and Netlify are working on verified adapters
built on the Adapter API
## Test plan
- [ ] Verify links resolve correctly (adapter API reference, test suite
anchor, ecosystem working group page)
- [ ] Confirm markdown table renders properly with the longer "Varies"
cell
- [ ] Review wording with stakeholders (Cloudflare, Netlify, Bun)
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Co-authored-by: Tim Neutkens <tim@timneutkens.nl>
