• Creates a global filter selector component for managing global filters
• This component allows selecting and updating filter values
• Uses mutable search to create a filter query string that can be appended to widget queries.
• Sets up placeholder callbacks for persisting changes later on.
• Note: Logic for persisting global filter changes will be in a separate PR

Try it out using this deployment: https://sentry-6pqpj4e2n.sentry.dev/issues/
This deployment is from changes made on top of this branch to add persistence (that way you can see the filter selector in action.

Fixes DAIN-929