frontend: improve joystick mapping reviews

### Current behaviour

It is easy to make custom joystick mappings, but not to know what has changed from the profile default, which makes it difficult to partially restore it while maintaining some of the changes.

#1962 introduces new sources of joystick mappings, which requires interface guidance when new options are available, and will also exacerbate the confusion as to which recommended functions:
1. have been changed,
2. have been removed entirely,
3. are currently mapped,
4. are mapped where intended, and/or
5. conflict between sources

### Expected or desired behaviour

Ideally we would have a unified changes+suggestions review interface, based around the familiar mapping configuration interface, while clearly displaying what has changed (and how), and allowing bulk applications of suggestions/defaults as well as partial modifications of a template:

The suggested interface includes:
- status indicators for which functions have been moved to a different button, removed entirely, or confirmed since the latest relevant suggestions were found
- configured/suggested options, coloured by source, with bulk "select" buttons for each source, and "all" for including overriding those which have already previously been confirmed (e.g. to restore everything to the profile default)
- stacked suggestions for each button, selectable with radio-buttons, and confirmable with an arrow button (to keep track of which ones have already been intentionally decided on)

### Prerequisites

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

Start with the existing joystick mapping configuration interface and review issue #1962 for the additional mapping sources. Done means a unified review flow shows changes, removals, current and conflicting mappings, supports source-based bulk selection and partial restoration, and records confirmed suggestions.

Written by the indexing model from the issue text.