ci(dependabot): use directories to group pull request by scope/dir and support globbing

[noirbizarre]

Now that dependabot/dependabot-core#2178 has been implemented and delived, we can use the directories option to group dependabot pull request by scope/directories.

This will:

• simplify Dependabot config (remove the need to list each nested directory)
• prevent missing update on nested directories (root directory as single directory option is not recursive and does not benefit from dependabot updates)
• reduce the number of pull-requests by code owners

Note

If no update is triggered, we might need to add /* to every double star pattern.

Note

Legacy actions (nexus, gemfury...) have been kept and will need separate pull requests for removal after checking they are not in use anymore

Warning

this might trigger some pull request for not up to date nested actions