[feat gw-api]remove ReplacePrefixMatch support

[shuqz]

Description

• due to ALB limitation (cannot preserve suffix), we cannot support ReplacePrefixMatch in Filter type: RequestRedirect. we can still support ReplaceFullPath
• added instruction in documentation
• reconcile will error out if user try to use ReplacePrefixMatch, e.g

{"level":"error","ts":"2025-11-18T01:23:03Z","msg":"Reconciler error","controller":"gateway.k8s.aws/alb","object":{"name":"same-namespace","namespace":"gateway-conformance-infra"},"namespace":"gateway-conformance-infra","name":"same-namespace","reconcileID":"","error":"ReplacePrefixMatch is not supported in RequestRedirect filters. ALB redirect actions cannot preserve path suffixes during prefix replacement. Use URLRewrite filter with ReplacePrefixMatch for path transformations, or use ReplaceFullPath in RequestRedirect for static path redirects"}

• modified e2e test too

Checklist

• Added tests that cover your change (if possible)
• Added/modified documentation as required (such as the README.md, or the docs directory)
• Manually tested
• Made sure the title of the PR is a good description that can go into the release notes

BONUS POINTS checklist: complete for good vibes and maybe prizes?! 🤯

• Backfilled missing tests for code in same general area 🎉
• Refactored something and made the world a better place 🌟

[k8s-ci-robot]

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This pull-request has been approved by: shuqz

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