IndexSet Templates UI

## To dos
- [x] remove legacy default configuration
- [x] add index set template tab
- [x] https://github.com/Graylog2/graylog2-server/pull/19381
- [x] add action to set default template
- [x] add built-in label
- [x] add default label
- [ ] Adjust/add E2E tests
- [ ] Validate index set template form on submit in the backend (and display error per field)

## UI Description
- Index sets page has a new tab to manage Index Set templates
- On Index Set templates tab we show
- a data table listing the configuration profiles with
- template name
- template description
- indicate whether it's the default template
- indicate whether it's a prebuilt template
- actions for each entry (edit, copy, delete, set default)
- When copying a template it opens the edit view of that template
- A button to create a new profile
- clicking the button leads to a form to create a new index set template (easiest to reuse existing form?)
- The form is validated when clicking save/create
- When creating a new index set the flow incorporates selecting a template

## Screenshots for context

## Restrictions:
- built-in templates cannot be selected as default
- built-in templates cannot be deleted
- default template cannot be deleted