Feature Request: Improvements to Speed in Playback Effects

### What problem does this address?

The control for speed is clunky. A slider would require fewer taps, especially with the preset "shortcuts only toggling between 1, 1.5, and 2.

I prefer 2.5 and 3 so it's a pain to adjust.

### What is your proposed solution?

2 things: a slider instead of a -/+ which requires a ton of taps to get where you want

Set preferred speed shortcuts in settings instead of having it stuck in 1, 1.5, and 2. Those can be defaults but you should be able to set it.

### Did you search for existing feature suggestions?

- [X] I have searched for existing feature suggestions.

Start by locating the playback speed control that currently uses -/+ buttons and the settings screen or storage used for playback preferences. Done means replacing the repeated-tap control with a slider and allowing users to configure preferred speed shortcuts, while retaining 1, 1.5, and 2 as defaults.

Written by the indexing model from the issue text.