cookie session: support 0 ttl (#32093)

* cookie session: support 0 ttl

Signed-off-by: Kuat Yessenov <kuat@google.com>

* add note

Signed-off-by: Kuat Yessenov <kuat@google.com>

* update changelog

Signed-off-by: Kuat Yessenov <kuat@google.com>

* review

Change-Id: I24b84f52cbe3617e5e298d89b4cafd3c76a62ec8
Signed-off-by: Kuat Yessenov <kuat@google.com>

* clarify doc

Change-Id: Ib88c98412a6fe696365a01e3f69a9198bf1b90e7
Signed-off-by: Kuat Yessenov <kuat@google.com>

* review

Change-Id: I81e461948b75eaee9ef909d8d13bf8fea7c66dc9
Signed-off-by: Kuat Yessenov <kuat@google.com>

---------

Signed-off-by: Kuat Yessenov <kuat@google.com>

Mirrored from https://github.com/envoyproxy/envoy @ 6354dcffc83153c96b9dbded64eb98a49fd6ad94

envoy/type/http/v3/cookie.proto

@@ -22,7 +22,7 @@ message Cookie {
   string name = 1 [(validate.rules).string = {min_len: 1}];
 
   // Duration of cookie. This will be used to set the expiry time of a new cookie when it is
-  // generated. Set this to 0 to use a session cookie.
+  // generated. Set this to 0s to use a session cookie and disable cookie expiration.
   google.protobuf.Duration ttl = 2 [(validate.rules).duration = {gte {}}];
 
   // Path of cookie. This will be used to set the path of a new cookie when it is generated.