CORS - Followup on suggested improvements

[rikatz]

What would you like to be added:
Followup on suggested improvements for CORS:

• https://github.com/kubernetes-sigs/gateway-api/pull/3739/files#r2667680110 - Fix header ordering, do not introduce the IgnoreWhiteSpace
• https://github.com/kubernetes-sigs/gateway-api/pull/3739/files#r2731132648 - Introduce HeaderAsList for the ordering validation
• https://github.com/kubernetes-sigs/gateway-api/pull/3739/files#r2690157156 - Followup on allowCredentials and wildcard usage for methods (this is a proxy behavior)

Why this is needed:
Move with CORS promotion during RC cut, and followup with implementations on conformance improvements

/cc @snorwin @DamianSawicki @zhaohuabing

[DamianSawicki]

For the third bullet point, here are the relevant sources:

• gateway-api/geps/gep-1767/index.md

  Lines 53 to 54 in b713c06

  	Credentials are cookies, TLS client certificates, or authentication headers containing a username and password.
  	A "credentialed request" is a request containing some credentials.

  (after https://developer.mozilla.org/en-US/docs/Web/API/RequestInit#credentials).
• https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CORS#credentialed_requests_and_wildcards

[jub0bs]

Perhaps have a look at relying on github.com/jub0bs/cors under the hood. 😉