Update AuthorizeFilter to no-op when AuthorizationMiddleware has run

[JamesNK]

No-op AuthorizeFilter when AuthorizationMiddleware has run for performance

Addresses #4216

[rynowak]

LGTM but get a signoff from @HaoK as well

[huan086]

Another minor performance improvement in CorsOptions

Instead of having to compute the hash key twice
return PolicyMap.ContainsKey(name) ? PolicyMap[name] : null;

Use
return PolicyMap.TryGetValue(name, out var policies) ? policies : null;