Add cluster recommendations API support to SDKs

[ArunGopinathan]

Adds support for the new tunnels Cluster Recommendations API across the C#, TypeScript, and Go SDKs (with generated contracts for Java and Rust). The SDK can now automatically select the best cluster for a new tunnel, optionally constrained by a required geography, while remaining fully backward compatible.

Contracts (C# source-of-truth, auto-generated to TS/Go/Java/Rust):

• ClusterAvailability, ClusterRecommendation, ClusterRecommendationResponse
• Generator: add float/double type mappings (TS/Go/Java/Rust writers)

What changed

• New management method — GetClusterRecommendations(preferredClusterId, requiredGeo) (C#/TS/Go, plus interface + mocks) returns ranked cluster recommendations.
• Auto-recommend on create — CreateTunnel now, when no cluster is specified, calls the recommendations API and creates the tunnel in the recommended cluster. Any failure is swallowed and the call falls back to normal global (Traffic Manager) routing. If a cluster is already set, the recommendations call is skipped.
• RequiredGeo request option — added to TunnelRequestOptions in all three SDKs. It is forwarded only on the recommendations request and is intentionally excluded from the create-tunnel query string.
• New contracts — ClusterAvailability, ClusterRecommendation, ClusterRecommendationResponse (generated for all languages from the C# source).

Notable fix

• Go buildUri aliasing bug — buildUri mutated the shared m.uri (*url.URL) in place. Latent before, but auto-recommend now sets ClusterID, which made the base URI get permanently pinned to the recommended cluster's host for all subsequent requests. Fixed by copying the URL by value; added a dedicated regression test.

Testing

• Unit tests: C# 136 passing · TS 81 passing · Go CreateTunnel suite passing (incl. new parity + regression tests covering: recommend-when-unset, skip-when-set, RequiredGeo forwarding, RequiredGeo excluded from create, and no base-URI mutation).
• Packaged E2E: Built the SDK to a local NuGet feed and ran a console consumer (referencing the package, not source) against a mock service — verified at runtime that auto-recommend issues the /clusters/recommendations GET first, creates the tunnel in the returned cluster, and deletes it; RequiredGeo rides the recommendations request and is absent from the create request.

Pre-PR checklist

• ✅ Go PackageVersion bumped 0.1.26 → 0.1.27 in go/tunnels/tunnels.go (per the patch-per-PR convention).
• ✅ TS package.json floors — connections and management already require @microsoft/dev-tunnels-contracts / -management at >1.3.50, which is greater than the current published 1.3.48. (CI rewrites these to concrete versions at publish time.) No change needed.

Compatibility

Fully backward compatible. Existing callers that set a cluster, or that don't, behave exactly as before — the only new behavior is automatic cluster selection when none is provided, with graceful fallback on any error.