* Gateway also needs global flattening

Signed-off-by: Benjamin Leggett <benjamin.leggett@solo.io>

* Relnote

Signed-off-by: Benjamin Leggett <benjamin.leggett@solo.io>

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Signed-off-by: Benjamin Leggett <benjamin.leggett@solo.io>

* Fix ambient telemetry in ingress gateways

Signed-off-by: Keith Mattix II <keithmattix@microsoft.com>

* Add tests

Signed-off-by: Keith Mattix II <keithmattix@microsoft.com>

* Fixup

Signed-off-by: Keith Mattix II <keithmattix@microsoft.com>

* Allow non-ambient usage of peer metadata discovery

Signed-off-by: Keith Mattix II <keithmattix@microsoft.com>

* Add release note

Signed-off-by: Keith Mattix II <keithmattix@microsoft.com>

* Only override peer discovery for ambient if unset

Signed-off-by: Keith Mattix II <keithmattix@microsoft.com>

* Make gen

Signed-off-by: Keith Mattix II <keithmattix@microsoft.com>

* Make metadata discovery explicit

Signed-off-by: Keith Mattix II <keithmattix@microsoft.com>

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Signed-off-by: Keith Mattix II <keithmattix@microsoft.com>

* PILOT_SEND_UNHEALTHY_ENDPOINTS: exclude terminating endpoints

The purpose of PILOT_SEND_UNHEALTHY_ENDPOINTS is to let envoy know about
the count of health and unhealth endpoints as a factor into its failover
decisions. For instance, if we have 5/10 pods health, it would failover.

This has problematic behavior during scaling up/down. For instance, if I
just have a single pod and then make a change, I will temporarily have 2
pods (the new one, and the old one terminating). Envoy will now see this
as 50% health and failover. This is bad -- its not actually unhealthy at
all!

Additionally, when pods are scaling down we end up keeping them as
unhealthy. Consider I have 1/2 pods healthy, and shut down the unhealthy
one but it takes a few minutes to fully terminate. During that time,
envoy will consider us 50% healthy. However, because we requested 1 pod
and have 1 pod, I would consider that 100% healthy.

----

This PR adds a new health mode, "terminating".
* When the feature flag is false, terminating and unhealthy mean the
  same thing -- do not send the endpoint to envoy. This has no impact.
* When the feature flag is true, we will not sending terminating
  endpoints. This means a terminating endpoint is not taken into account
for the health calculations.

This change does not impact whether we send traffic to the terminating
pods or not -- both before and after, we never do this.

Note: there is another status, 'draining', which is a very specialized
mode that is only used when session persistence is enabled on a service
&& the endpoint is terminating && it used to be healthy. Comments in the
code clarify the differences between these two similar states. These
endpoints *are* sent to envoy and traffic is sent to them, so its
fundamentally different than Terminating.

* add NDS test

* add note

… relnotes (#54697)

* Be more explicit about how Helm value deprecations should manifest in relnotes

Signed-off-by: Benjamin Leggett <benjamin.leggett@solo.io>

* fix

Signed-off-by: Benjamin Leggett <benjamin.leggett@solo.io>

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Signed-off-by: Benjamin Leggett <benjamin.leggett@solo.io>