[8.19] (backport #8104) [k8s tests] Add versions + comments explaining why (#8127)

* [k8s tests] Add versions + comments explaining why (#8104)

* Add versions + comments explaining why

* Update .buildkite/bk.integration.pipeline.yml

Co-authored-by: Panos Koutsovasilis <[email protected]>

* Remove version no longer supported by EKS

* Remove version not supported by Elastic Agent Helm Chart

* Reference support matrix for rationale

---------

Co-authored-by: Panos Koutsovasilis <[email protected]>
(cherry picked from commit 78d5d2e)

# Conflicts:
#	.buildkite/bk.integration.pipeline.yml

* Fixing conflicts

---------

Co-authored-by: Shaunak Kashyap <[email protected]>

Author: mergify[bot]

.buildkite/bk.integration.pipeline.yml

@@ -339,13 +339,18 @@ steps:
           setup:
             variants:
             - "basic,wolfi,complete,complete-wolfi,service,cloud"
+
+            # See the Kubernetes Compatible Versions for Elastic Agent in the Elastic
+            # Support Matrix (https://www.elastic.co/support/matrix#matrix_kubernetes) for
+            # the rationale on why these specific versions are chosen.
             version:
-            - v1.27.16
-            - v1.28.9
-            - v1.29.8
-            - v1.30.8
-            - v1.31.0
-            - v1.32.0
+              - v1.27.16
+              - v1.28.15
+              - v1.29.14
+              - v1.30.0
+              - v1.31.0
+              - v1.32.0
+              - v1.33.0
 
   - label: ESS stack cleanup
     depends_on: