Ability to search for ideas that have not yet been linked to projects

Is your feature request related to a problem? Please describe.
If the administrator manually creates projects for budgets, it can be hard to determine which accepted ideas have not yet been linked to any project. This makes setting up the budgeting phase cumbersome when there is a large number of ideas.

Describe the solution you'd like
The search panel should provide a filtering option to find the projects that have been either linked or not yet linked to any projects. Potentially this could also allow searching links in other components, such as accountability.

Describe alternatives you've considered
Manually finding the ideas from the console.

Additional context
This is an actual user request from a Decidim administrator.

Does this issue could impact on users private data?
No.

Funded by
N/A