`theme` crate spring cleaning (#18695)

This PR does some spring cleaning on the `theme` crate:

- Removed two unused stories and the story dep
- Removed the `one` theme family (from the `theme` crate, not the app),
this is now `zed_default_themes`.
- This will hopefully remove some confusion caused by this theme we
started in rust but didn't end up using
- Removed `theme::prelude` (it just re-exported scale colors, which we
don't use outside `theme`)
- Removed completely unused `zed_pro` themes (we started on these during
the gpui2 port and didn't finish them.)

Release Notes:

- N/A

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Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>