Document trusted-server.example.toml and restore dropped-but-supported config sections

[aram356]

Summary

trusted-server.example.toml is the source-controlled config template (ts config init, and embedded into the Cloudflare/Spin adapters via include_str!). Over time it drifted from the supported config schema: it dropped several sections that still exist in the Rust config structs, and it doesn't clearly distinguish the required minimum config from optional/vendor settings.

Problems

• No clear "minimum config". Nothing in the file signals that only [publisher], [ec].passphrase, and an admin-covering [[handlers]] are required to boot/validate. [ec] in particular is easy to assume optional, but an omitted/empty passphrase fails validation.
• Dropped-but-still-supported sections. The following map to live structs yet were missing from the template: [tester_cookie], [rewrite], the [consent] tree, [image_optimizer], [tinybird], [integrations.osano], publisher.max_buffered_body_bytes, sourcepoint.auth_cookie_name, DataDome protection fields, Prebid override rules.
• Sparse descriptions. Most keys have no explanation of what they do or their defaults.

Proposed change

• Keep the required trio active with per-key descriptions.
• Comment out every optional section/integration, each with a one-line description, so a fresh deploy starts minimal and safe.
• Re-add the dropped-but-supported sections as documented (commented) blocks.
• Keep the four ts audit-patched integrations (gpt, didomi, datadome, google_tag_manager) active with enabled = false so the audit CLI can still flip them.
• Keep all example hosts as example.com (no real vendor domains).

Acceptance

• File deserializes and passes Settings::from_toml validation (verified with real secrets substituted for the intentional placeholders).
• ts audit draft-config patching still works (run_audit_writes_selected_outputs_and_summary).
• Config schema in the file matches the actual Rust structs.