[Asset Inventory][Azure] Add missing resources and ECS fields required for GA

[kubasobon]

Summary of your changes

This PR:

• Adds Azure Entra Group fetcher (previously missing)
• Adds Azure Entra User fetcher (previously missing)
• Adds Azure Entra Role Definition fetcher (previously missing)
• Re-classifies Azure Principal to match Cloud Assets spreadsheet
• Introduces Group, Organization, and Tags ECS fields to Asset model
• Adds all required & available ECS fields to assets, except for Role and Principal where it is impossible to test right now
• Updates unit tests where applicable

Outstanding issues ⚠️

The PR does not address all taxonomy issues and skips filling ECS fields for Role and Principal. A follow-up ticket will be created.

Related Issues

Closes https://github.com/elastic/security-team/issues/11690

Checklist

• I have added tests that prove my fix is effective or that my feature works
• I have added the necessary README/documentation (if appropriate)

[mergify]

This pull request does not have a backport label. Could you fix it @kubasobon? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-v./d./d./d is the label to automatically backport to the 8./d branch. /d is the digit
  NOTE: backport-v8.x has been added to help with the transition to the new branch 8.x.

[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
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 asset-inv-azure-ga upstream/asset-inv-azure-ga
git merge upstream/main
git push upstream asset-inv-azure-ga

[kubasobon]

As for coveralls, it fails on internal/resources/providers/msgraph/provider.go, which I tried wrapping in unit tests, but I gave up on it since the upstream SDK is auto-generated and does not lend itself to testing.