### Problem statement

We have a number of occurences of "grey boxes" around the primerized part of the application, that were all handcrafted, but followed the same recipe. Since we want to ensure consistent looks around the application, a common component should be extracted for these components, including usage instructions.

Occurences look like this mostly:

```ruby
Primer::Box.new(border: true, border_radius: 2, bg: :inset, p: 3)
```

### Acceptance criteria

* Extract common component for these "inset" elements (e.g. named `InsetBox`)

* Begin of the insertionComponentEnd of the insertion Begin of the deletion componentEnd of the deletion has opinionated defaults according to current Begin of the insertionimplementation

* AllowsEnd of the insertion Begin of the deletion implementation, but allows toEnd of the deletion overwrite:

* Begin of the insertionBorder: true/falseEnd of the insertion Begin of the deletion _**to be defined**_End of the deletion

* Component is properly documented in Lookbook


### Occurences

* [Projects::CopyFormComponent](https://github.com/opf/openproject/blob/dev/app/components/projects/copy_form_component.html.erb#L35-L37) (exactly the same)

* [Projects::NewComponent](https://github.com/opf/openproject/blob/dev/app/components/projects/new_component.html.erb) (exactly the same)

* [Projects::SourceProjectSelectComponent](https://github.com/opf/openproject/blob/dev/app/components/projects/source_project_select_component.html.erb) (exactly the same)

* [Projects::TemplateSelectComponent](https://github.com/opf/openproject/blob/dev/app/components/projects/template_select_component.html.erb)  (exactly the same)

* [ProjectQueries::PublicFlagComponent](https://github.com/opf/openproject/blob/dev/app/components/shares/project_queries/public_flag_component.html.erb) (exactly the same)

* [MeetingAgendaItems::Outcomes::ShowNotesComponent](https://github.com/opf/openproject/blob/dev/modules/meeting/app/components/meeting_agenda_items/outcomes/show_notes_component.html.erb) (not exactly the same style, but pretty close)

* different padding at the bottom

* background color added via CSS (and might be a different shade of grey, `inset` vs. `muted`)

* [WorkPackageMeetingsTab::MeetingAgendaItemComponent](https://github.com/opf/openproject/blob/dev/modules/meeting/app/components/work_package_meetings_tab/meeting_agenda_item_component.html.erb) (not exactly the same style)

* background color added via CSS (and might be a different shade of grey, `inset` vs. `muted`)