Improve location programming API

Is your feature request related to a problem? Please describe.
If a user wants to propose something in multiple areas for example, it's hard to mark the specific spots only using one marker to the general area. So adding multiple markers would solve this issue.

Also location adding is already used in proposals and budgets. Soon it will probably going to be used in even more components. The way it's implemented now is component specific, when the logic could be done in one place and used in multiple components.

Describe the solution you'd like

The possibility to add multiple locations to a record instead of one and moving the location adding -logic to one place.

Additional context

The backbone for this logic can already be found in this module: https://github.com/mainio/decidim-module-locations

Could this issue impact on users private data?

No