Fix OSS Fuzz crashes due to validation issues in RBAC Config (#12757)

Added validation that action enum is within range

Risk Level: low
Testing: passes added regression tests
Docs Changes: N/A
Release Notes: N/A

Fixes: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=24824&sort=-opened&can=1&q=proj%3Aenvoy%20status%3DNew

Signed-off-by: Zach Reyes <zasweq@google.com>

Mirrored from https://github.com/envoyproxy/envoy @ aecd2459f70a8f7ce6032a0e8fc7e9a8d04e9798

envoy/config/rbac/v3/rbac.proto

@@ -101,7 +101,7 @@ message RBAC {
   //    key namespace 'envoy.common'. If no policies match, it is set to `false`.
   //    Other actions do not modify this key.
   //
-  Action action = 1;
+  Action action = 1 [(validate.rules).enum = {defined_only: true}];
 
   // Maps from policy name to policy. A match occurs when at least one policy matches the request.
   map<string, Policy> policies = 2;

envoy/config/rbac/v4alpha/rbac.proto

@@ -100,7 +100,7 @@ message RBAC {
   //    key namespace 'envoy.common'. If no policies match, it is set to `false`.
   //    Other actions do not modify this key.
   //
-  Action action = 1;
+  Action action = 1 [(validate.rules).enum = {defined_only: true}];
 
   // Maps from policy name to policy. A match occurs when at least one policy matches the request.
   map<string, Policy> policies = 2;