(docs/dualstack): v1.17 updates (#17457)

* Add placehold doc updates for dualstack in 1.17

Signed-off-by: Lachlan Evenson <lachlan.evenson@microsoft.com>

* Add Downward API and /etc/hosts Pod IP validation

Signed-off-by: Lachlan Evenson <lachlan.evenson@microsoft.com>

* remove addressed known issue via k/k pr 85246

Signed-off-by: Lachlan Evenson <lachlan.evenson@microsoft.com>

* Remove known issue and add flag as part of k/k 79993

Signed-off-by: Lachlan Evenson <lachlan.evenson@microsoft.com>

* remove follow up placeholders

Signed-off-by: Lachlan Evenson <lachlan.evenson@microsoft.com>

* Update verbiage

Signed-off-by: Lachlan Evenson <lachlan.evenson@microsoft.com>

* Make IP addressing consistent throughout the task

Signed-off-by: Lachlan Evenson <lachlan.evenson@microsoft.com>

* Update to status.podIPs

Signed-off-by: Lachlan Evenson <lachlan.evenson@microsoft.com>

* Update content/en/docs/tasks/network/validate-dual-stack.md

Use set instead of env

Co-Authored-By: Khaled Henidak (Kal) <khnidk@outlook.com>

content/en/docs/concepts/services-networking/dual-stack.md

@@ -51,6 +51,7 @@ To enable IPv4/IPv6 dual-stack, enable the `IPv6DualStack` [feature gate](/docs/
       * `--feature-gates="IPv6DualStack=true"`
       * `--cluster-cidr=<IPv4 CIDR>,<IPv6 CIDR>` eg. `--cluster-cidr=10.244.0.0/16,fc00::/24`
       * `--service-cluster-ip-range=<IPv4 CIDR>,<IPv6 CIDR>`
+      * `--node-cidr-mask-size-ipv4|--node-cidr-mask-size-ipv6` defaults to /24 for IPv4 and /64 for IPv6
    * kubelet:
       * `--feature-gates="IPv6DualStack=true"`
    * kube-proxy:
@@ -98,9 +99,7 @@ The use of publicly routable and non-publicly routable IPv6 address blocks is ac
 
 ## Known Issues
 
-   * IPv6 network block assignment uses the default IPv4 CIDR block size (/24)
    * Kubenet forces IPv4,IPv6 positional reporting of IPs (--cluster-cidr)
-   * Dual-stack networking does not function if the `EndpointSlice` feature gate is enabled.
 
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