frontend: `VeryGenericIndicator` configuration is inconsistent

### Current behaviour

1. Variable selection involves clicking a button, typing into a (new, different location) search bar, then selecting options from another separate location
2. Variables are presented by their Cockpit IDs

### Expected or desired behaviour

1. Use `v-autocomplete`, per #1811
2. Use variable names, instead of their IDs

### Prerequisites

- [x] I have checked to make sure that a similar request has not already been filed or fixed.

Start by locating the frontend implementation of `VeryGenericIndicator` and read the related request in #1811. Trace the current variable-selection UI and identify where Cockpit IDs are displayed; done means using the requested autocomplete interaction and showing variable names instead of IDs.

Written by the indexing model from the issue text.