Create a general moderation panel

**Is your feature request related to a problem? Please describe.**

The problem being that when you are a global admin and want to have an overview on reported content, you need to go in each space to perform moderation actions. Having a first level tab in the admin panel where you can see all incoming reported content would make it easier for global admins to have an overview on reported contents and moderations.

• The central moderation tab could be displayed on the primary navbar in Back-End
• The reported and hidden content could be separated in two different panels, thanks to two tabs in administrator secondary navbar.
• Content that appear should be based on the user roles and the spaces they access to : Global admin sees everything, Moderators only see content from the space they were added to (can be multiple ones)

**Describe the solution you'd like**

Keep moderation panels siloted.

**Describe alternatives you've considered**

A clear and concise description of any alternative solutions or features you've considered.

**Additional context**

See : https://meta.decidim.org/processes/roadmap/f/122/proposals/15628 **Does this issue could impact on users private data?**

No

**Funded by**

EU Commission