Fixes#15834
## Migration Guide
The APIs of `Time`, `Timer` and `Stopwatch` have been cleaned up for
consistency with each other and the standard library's `Duration` type.
The following methods have been renamed:
- `Stowatch::paused` -> `Stopwatch::is_paused`
- `Time::elapsed_seconds` -> `Time::elasped_secs` (including `_f64` and
`_wrapped` variants)
# Objective
What's that? Another PR for the grand migration to required components?
This time, audio!
## Solution
Deprecate `AudioSourceBundle`, `AudioBundle`, and `PitchBundle`, as per
the [chosen
proposal](https://hackmd.io/@bevy/required_components/%2Fzxgp-zMMRUCdT7LY1ZDQwQ).
However, we cannot call the component `AudioSource`, because that's what
the stored asset is called. I deliberated on a few names, like
`AudioHandle`, or even just `Audio`, but landed on `AudioPlayer`, since
it's probably the most accurate and "nice" name for this. Open to
alternatives though.
---
## Migration Guide
Replace all insertions of `AudioSoucreBundle`, `AudioBundle`, and
`PitchBundle` with the `AudioPlayer` component. The other components
required by it will now be inserted automatically.
In cases where the generics cannot be inferred, you may need to specify
them explicitly. For example:
```rust
commands.spawn(AudioPlayer::<AudioSource>(asset_server.load("sounds/sick_beats.ogg")));
```
Created soundtrack example, fade-in and fade-out features, added new
assets, and updated credits.
# Objective
- Fixes#12651
## Solution
- Created a resource to hold the track list.
- The audio assets are then loaded by the asset server and added to the
track list.
- Once the game is in a specific state, an `AudioBundle` is spawned and
plays the appropriate track.
- The audio volume starts at zero and is then incremented gradually
until it reaches full volume.
- Once the game state changes, the current track fades out, and a new
one fades in at the same time, offering a relatively seamless
transition.
- Once a track is completely faded out, it is despawned from the app.
- Game state changes are simulated through a `Timer` for simplicity.
- Track change system is only run if there is a change in the
`GameState` resource.
- All tracks are used according to their respective licenses.
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
