Add jitter to strict and logical dns clusters (#35745)

Resolves #35641. Adding DNS jitter to resolvers makes it so that envoy
doesnt stampede the DNS server when it has multiple entries with the
same expiration.

 Testing is still WIP. I am open to any suggestions.

Commit Message: dns: add jitter to strict dns
Additional Description:
Risk Level: low
Testing: unit tests
Docs Changes:
Release Notes:
for the :ref:`strict DNS
<arch_overview_service_discovery_types_strict_dns>` and :ref:`logical
DNS
    <arch_overview_service_discovery_types_logical_dns>` cluster types,
the new :ref:`dns_jitter
<envoy_v3_api_field_config.cluster.v3.Cluster.dns_jitter>` field, if
provided, will causes the cluster to refresh DNS entries later by a
random amount of time as to
avoid stampedes of DNS requests. This field sets the upper bound
(exclusive) for the random amount.
Platform Specific Features:
[Optional Runtime guard:]
[Optional Fixes #Issue]
[Optional Fixes commit #PR or SHA]
[Optional Deprecated:]
[Optional [API
Considerations](https://github.com/envoyproxy/envoy/blob/main/api/review_checklist.md):]

---------

Signed-off-by: Steven Jin Xuan <sjinxuan@microsoft.com>
Signed-off-by: Steven Jin <stevenjin8@gmail.com>
Co-authored-by: Adi (Suissa) Peleg <adip@google.com>

Mirrored from https://github.com/envoyproxy/envoy @ 20e27887d29d735e1cc47cbb9af1cfe9baac4b4d

envoy/config/cluster/v3/cluster.proto

@@ -45,7 +45,7 @@ message ClusterCollection {
 }
 
 // Configuration for a single upstream cluster.
-// [#next-free-field: 58]
+// [#next-free-field: 59]
 message Cluster {
   option (udpa.annotations.versioning).previous_message_type = "envoy.api.v2.Cluster";
 
@@ -956,6 +956,17 @@ message Cluster {
   google.protobuf.Duration dns_refresh_rate = 16
       [(validate.rules).duration = {gt {nanos: 1000000}}];
 
+  // DNS jitter can be optionally specified if the cluster type is either
+  // :ref:`STRICT_DNS<envoy_v3_api_enum_value_config.cluster.v3.Cluster.DiscoveryType.STRICT_DNS>`,
+  // or :ref:`LOGICAL_DNS<envoy_v3_api_enum_value_config.cluster.v3.Cluster.DiscoveryType.LOGICAL_DNS>`.
+  // DNS jitter causes the cluster to refresh DNS entries later by a random amount of time to avoid a
+  // stampede of DNS requests. This value sets the upper bound (exclusive) for the random amount.
+  // There will be no jitter if this value is omitted. For cluster types other than
+  // :ref:`STRICT_DNS<envoy_v3_api_enum_value_config.cluster.v3.Cluster.DiscoveryType.STRICT_DNS>`
+  // and :ref:`LOGICAL_DNS<envoy_v3_api_enum_value_config.cluster.v3.Cluster.DiscoveryType.LOGICAL_DNS>`
+  // this setting is ignored.
+  google.protobuf.Duration dns_jitter = 58;
+
   // If the DNS failure refresh rate is specified and the cluster type is either
   // :ref:`STRICT_DNS<envoy_v3_api_enum_value_config.cluster.v3.Cluster.DiscoveryType.STRICT_DNS>`,
   // or :ref:`LOGICAL_DNS<envoy_v3_api_enum_value_config.cluster.v3.Cluster.DiscoveryType.LOGICAL_DNS>`,