Remove the DNS over HTTPS (DoH) proxy feature built on CoreDNS due to
security vulnerabilities (GO-2025-3942, GO-2026-4289).
This removes:
- Standalone proxy-dns command (cloudflared proxy-dns)
- Tunnel subcommand (cloudflared tunnel proxy-dns)
- Proxy-dns flags for tunnel run (--proxy-dns, --proxy-dns-port, etc.)
- Config file resolver section support
- tunneldns/ package (CoreDNS-based implementation)
- Related component tests
BREAKING CHANGE: The proxy-dns feature is no longer available.
Users should migrate to alternative DNS over HTTPS solutions.
- Move packages the provide generic functionality (such as config) from `cmd` subtree to top level.
- Remove all dependencies on `cmd` subtree from top level packages.
- Consolidate all code dealing with token generation and transfer to a single cohesive package.
João "Pisco" Fernandes
Igor Postelnik
Areg Harutyunyan
Dalton