[Azure docs] Add Azure monitoring docs

[alaudazzi]

This PR creates a new Azure monitoring section that includes:

• the existing Azure tutorials, Monitor Microsoft Azure with Elastic Agent, Monitor Microsoft Azure with the Azure Native ISV Service, Monitor Microsoft Azure with Beats, that are currently under Tutorials.
• a new use case on how to collect any metrics using the generic Azure Monitor integration
  Relates to [Azure docs] Add a new section on Azure monitoring #3742

Here is a doc preview of the current status.

[github-actions]

A documentation preview will be available soon.

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[mergify]

This pull request is now in conflict. Could you fix it @alaudazzi? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b azure-monitoring upstream/azure-monitoring
git merge upstream/main
git push upstream azure-monitoring