Implement AutoHostRewrite functionality in request handling

[Eeshu-Yadav]

Problem Description

The AutoHostRewrite feature was configured in the route configuration but not actually implemented in the request handling code. When a route was configured with AutoHostRewrite, the authority/host header should be automatically rewritten based on the upstream cluster, but this functionality was completely ignored during request processing.

Current State

✅ Configuration: AuthorityRewriteSpecifier::AutoHostRewrite was properly parsed from Envoy configuration
✅ Boolean Logic: The boolean logic for enabling/disabling AutoHostRewrite was fixed in PR #86
❌ Request Handling: The authority_rewrite field in RouteAction was not used during request processing

Related

• Fixes issue mentioned in PR Fix :Envoy Go control plane adaptation issues #86 review by @hzxuzhonghu
• Similar to how PathRewriteSpecifier is implemented and working correctly