Migrate transfer group/project dropdown to `GlCollapsableListbox`

Proposal

GlCollapsableListbox is preferable to GlDropdown. We should migrate groups_projects/components/transfer_locations.vue to GlCollapsableListbox

Implementation guide

See !168258 (closed) for starting point. We realized that GlCollapsableListbox did not yet support infinite scroll for grouped options so need to first complete gitlab-ui#2921 (closed)

• Change search placeholder text to Search (minimum 3 characters)