Add unit test for mode/authentication to cover ConstructSdsSecretConfigWithCustomUds, ConstructValidationContext, ApplyCustomSDSToCommonTLSContext (#25306)
Add unit test for mode/authentication to cover ConstructSdsSecretConfigWithCustomUds, ConstructValidationContext, ApplyCustomSDSToCommonTLSContext (#25306)

* add unit test for authz and fix lint issue

* fix comments

* fix comments

* resolve comments
istio/istio,istio/istio,istio/istio,istio/istio,istio/istio