feat(backup-reports): rewrite with Handlebars

[b-Nollet]

Description

Rewriting backup reports with Handlebars.

There are still issues about handlebars blocks not being indented, which make the code less readable, but I did not find any solution to this problem (but it only affect code readability, not the output).

Checklist

• Commit
  • Title follows commit conventions
  • Reference the relevant issue (Fixes #007, See xoa-support#42, See https://...)
  • If bug fix, add Introduced by
• Changelog
  • If visible by XOA users, add changelog entry
  • Update "Packages to release" in CHANGELOG.unreleased.md
• PR
  • If UI changes, add screenshots
  • If not finished or not tested, open as Draft

[pdonias]

LGTM, please rebase to fix conflicts, test again with latest changes (I haven't tested myself) and if everything is ok, undraft the PR, assign me and I'll merge it.