This PR formalizes design components with the Component and
ComponentPreview traits.
You can open the preview UI with `workspace: open component preview`.
Component previews no longer need to return `Self` allowing for more
complex previews, and previews of components like `ui::Tooltip` that
supplement other components rather than are rendered by default.
`cargo-machete` incorrectly identifies `linkme` as an unused dep on
crates that have components deriving `IntoComponent`, so you may need to
add this to that crate's `Cargo.toml`:
```toml
# cargo-machete doesn't understand that linkme is used in the component macro
[package.metadata.cargo-machete]
ignored = ["linkme"]
```
Release Notes:
- N/A
---------
Co-authored-by: Marshall Bowers <git@maxdeviant.com>

- Adds the Switch component
- Updates `Selected`, `Selectable` -> `ToggleState`, `Toggleable`
- Adds `checkbox` and `switch` functions to align better with other
elements in our layout system.
We decided not to merge Switch and Checkbox. However, in a followup I'll
introduce a Toggle or AnyToggle enum so we can update
`CheckboxWithLabel` -> `ToggleWithLabel` as this component will work
exactly the same with either a Checkbox or a Switch.
Release Notes:
- N/A
Similar to https://github.com/zed-industries/zed/pull/18690 &
https://github.com/zed-industries/zed/pull/18695, this PR enables
required docs for `ui` and does some cleanup.
Changes:
- Enables the `deny(missing_docs)` crate-wide.
- Adds `allow(missing_docs)` on many modules until folks pick them up to
document them
- Documents some modules (all in `ui/src/styles`)
- Crate root-level organization: Traits move to `traits`, other misc
organization
- Cleaned out a bunch of unused code.
Note: I'd like to remove `utils/format_distance` but the assistant panel
uses it. To move it over to use the `time_format` crate we may need to
update it to use `time` instead of `chrono`. Needs more investigation.
Release Notes:
- N/A