Kubernetes upgrade from ver 1.28 to 1.29

[zhoujing2022]

Description
Currently kyma supports k8s 1.28. As all dependencies are met we can support the next version 1.29.

SRE k8s upgrade plan: https://wiki.one.int.sap/wiki/pages/viewpage.action?pageId=3011925416

Furthermore the support for next version should be prepared by already having a post-main-k3d-k8s-preview pipeline in place to identify problems fast and start addressing them.

Tasks

• [k8s update] @tw Pre-Notification to Customers via What's New. This Step must be done 4 weeks before Golive on PRD. (Before 14.July.2024)
• [k8s update] @zhoujing2022 Ensure no deprecated resources exist which will be no longer support on the new K8s cluster
• [k8s update] @neighbors Prow jobs are based on k8s 1.29 (see neighbours issue)
• [k8s update] @neighbors Already existing release jobs (from last release) should be still using old k8s version. (see neighbours issue)
• [k8s update] @neighbors Default version for kubectl is 1.29 (Docu, Prow) (see neighbours issue)
• [k8s update] @tw document new version and add release notes ()

AC:

• all pipelines are upgraded to k8s 1.29
• documentation is updated
• migration guide with potential manual actions is ready
• there is a new k3d based pipeline running on k8s 1.30 for preview purposes

The list of pre-tasks:
(POs analyze "Kubernetes Removals, Deprecations, and Major Changes in 1.29" - and create/add the issues below. These Issues must be released before 13.July.2024 on PRD.)
No Update from the teams.

Teams	Issues

Previous upgrade: #18558

Depends on kyma-project/test-infra#6109