Hide Custom Fields from Field Picker lists when not shared with the End User

Title: Hide custom fields from filter/view/grouping field pickers when the user has no access to the custom form

Current behaviour: Field pickers in filters, views and groupings, including Browse fields in the new filter experience and enhanced lists, list every active custom field for the object type, whether or not the custom form is shared with the user. Restricted fields on access levels only blank out the values; the field names stay visible.

Desired behaviour: Respect custom form sharing (or offer an access-level option) so that fields on forms a user can’t view are left out of field pickers entirely.

Why: In multi-team instances, users are shown dozens or hundreds of irrelevant fields, which hurts adoption and causes confusion. Field names can also be sensitive on their own (e.g. HR or financial fields).