DOCTEAM-1777: HA maintenance tasks

[tahliar]

PR creator: Description

Here's the articles for performing HA maintenance tasks, based on https://documentation.suse.com/sle-ha/15-SP7/html/SLE-HA-all/cha-ha-maintenance.html Sorry it's another big PR!

I've restructured the content into workflows instead of just a list of methods. Each method is a separate topic because they can be arranged into different workflows depending on what you're doing, and I might need to use them later in combination with SLES tasks. This structure meant I needed a generic "Perform the tasks" section in the middle, which I've included as a glue task.

PDFs:

Performing maintenance tasks on cluster infrastructure: HA-maintenance-performing-tasks-cluster-infra_en.pdf

Performing maintenance tasks on cluster nodes: HA-maintenance-performing-tasks-cluster-nodes_en.pdf

Performing maintenance tasks on cluster resources: HA-maintenance-performing-tasks-cluster-resources_en.pdf

PR creator: Are there any relevant issues/feature requests?

• jsc#DOCTEAM-1777

PR reviewer: Checklist for editorial review

Apart from the usual checks, please double-check also the following:

• do any new files fulfill the naming conventions specified in https://github.com/SUSE/doc-modular/blob/main/templates/README.md?
• article title/structure title: does it have the required length and does it use sentence style capitalization?
• revhistory: is it up-to-date and does it follow the guidelines specified in https://documentation.suse.com/style/current/html/style-guide-db/sec-smartdocs.html#sec-revhistory?
• metadata: does it follow the guidelines specified in https://documentation.suse.com/style/current/html/style-guide-db/sec-smartdocs.html#sec-taglist-smartdocs?