Update ECH known issue and add one entry about 8.17 upgrade (#4197)

<!--
Thank you for contributing to the Elastic Docs! 🎉
Use this template to help us efficiently review your contribution.
-->

## Summary
<!--
Describe what your PR changes or improves.  
If your PR fixes an issue, link it here. If your PR does not fix an
issue, describe the reason you are making the change.
-->

## Generative AI disclosure
<!--
To help us ensure compliance with the Elastic open source and
documentation guidelines, please answer the following:
-->
1. Did you use a generative AI (GenAI) tool to assist in creating this
contribution?
- [ ] Yes  
- [x] No  
<!--
2. If you answered "Yes" to the previous question, please specify the
tool(s) and model(s) used (e.g., Google Gemini, OpenAI ChatGPT-4, etc.).

Tool(s) and model(s) used:
-->

## Description

This is to address https://github.com/elastic/docs-content/issues/4195.
Some additional context in [an internal
ticket](elastic/support-tech-lead#1658 (comment)).

Two main aspects
* Add 8.17 version block as known issue
* Add "refer to known issue page" into deployment upgrade page

## Preview before PR merge

Known issue page:

[deploy-manage/deploy/elastic-cloud/restrictions-known-problems.md](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/4197/deploy-manage/deploy/elastic-cloud/restrictions-known-problems)

Upgrade your deployment page:

[deploy-manage/upgrade/deployment-or-cluster.md](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/4197/deploy-manage/upgrade/deployment-or-cluster)

## Preview after PR merge

Known issue page:

https://www.elastic.co/docs/deploy-manage/deploy/elastic-cloud/restrictions-known-problems

Upgrade your deployment page:
https://www.elastic.co/docs/deploy-manage/upgrade/deployment-or-cluster

---

cc @milanage @hisashinz

---------

Co-authored-by: Vlada Chirmicci <vlada.chirmicci@elastic.co>

Author: kunisen

deploy-manage/deploy/elastic-cloud/restrictions-known-problems.md

@@ -12,6 +12,7 @@ products:
 
 When using {{ecloud}}, there are some limitations you should be aware of:
 
+* [Stack versions](#ec-stack-versions)
 * [Security](#ec-restrictions-security)
 * [APIs](#ec-restrictions-apis)
 * [Transport client](#ec-restrictions-transport-client)
@@ -33,6 +34,11 @@ For limitations related to logging and monitoring, check the [Restrictions and l
 
 To learn more about the features that are supported by {{ecloud}}, check [{{ecloud}} Subscriptions](https://www.elastic.co/cloud/elasticsearch-service/subscriptions?page=docs&placement=docs-body).
 
+## Stack versions [ec-stack-versions]
+
+* Due to a known issue with the {{stack}}, certain upgrade paths to and from version 8.17 are currently blocked or disabled. Review [this KB article](https://support.elastic.co/knowledge/7c3ad709) for more guidance on the known issue. Additionally, review [this KB article](https://support.elastic.co/knowledge/e87d76a5) for detailed information regarding the specific versions affected. 
+
+
 
 ## Security [ec-restrictions-security]
 

deploy-manage/upgrade/deployment-or-cluster.md

@@ -29,6 +29,8 @@ This section contains the upgrade instructions for {{es}} clusters and {{kib}} i
 
 Before proceeding with the upgrade, review the [Plan your upgrade](/deploy-manage/upgrade/plan-upgrade.md) guidance to understand compatibility and timing considerations, and follow the steps in [Prepare to upgrade](/deploy-manage/upgrade/prepare-to-upgrade.md) to get your environment ready for the upgrade.
 
+Additionally, review the [Restrictions and known problems](../deploy/elastic-cloud/restrictions-known-problems.md) section to gain a comprehensive understanding of the known issues in {{ech}}. 
+
 If you’re still running {{stack}} version 7.17 or earlier, refer to the [Upgrade from 7.17 guide](/deploy-manage/upgrade/deployment-or-cluster/upgrade-717.md) for detailed guidance on planning and executing the upgrade to the latest {{version.stack}} release.
 
 ## Out-of-order releases [out-of-order-releases]