fix jwt_authn fuzzer crash on invalid provider URI (#34567)

* fix jwt_authz fuzzer crash on invalid provider URI

Signed-off-by: antoniovleonti <leonti@google.com>

* move validation to filter_config.cc

Signed-off-by: antoniovleonti <leonti@google.com>

* fix tests

Signed-off-by: antoniovleonti <leonti@google.com>

* add runtime guard

Signed-off-by: antoniovleonti <leonti@google.com>

* remote erroneous runtime guard

Signed-off-by: antoniovleonti <leonti@google.com>

* fix runtime feature name & add test

Signed-off-by: antoniovleonti <leonti@google.com>

---------

Signed-off-by: antoniovleonti <leonti@google.com>
Signed-off-by: Antonio V. Leonti <53806445+antoniovleonti@users.noreply.github.com>

Mirrored from https://github.com/envoyproxy/envoy @ 2917f74c28534634c021f3d86552891d45daa827

envoy/extensions/filters/http/jwt_authn/v3/config.proto

@@ -395,7 +395,7 @@ message RemoteJwks {
   //      cluster: jwt.www.googleapis.com|443
   //      timeout: 1s
   //
-  config.core.v3.HttpUri http_uri = 1;
+  config.core.v3.HttpUri http_uri = 1 [(validate.rules).message = {required: true}];
 
   // Duration after which the cached JWKS should be expired. If not specified, default cache
   // duration is 10 minutes.