Restructure ui into just elements and components (#3023)

This PR restructures the `ui` crate into just `elements` and
`components`.

This was already done on the `gpui2-ui` branch, just getting it onto
`main`.

Release Notes:

- N/A

---------

Co-authored-by: Nate Butler <nate@zed.dev>

crates/ui/src/elements/icon_button.rs

@@ -1,80 +0,0 @@
-use gpui2::elements::div;
-use gpui2::style::{StyleHelpers, Styleable};
-use gpui2::{Element, IntoElement, ParentElement, ViewContext};
-
-use crate::{icon, theme, IconColor};
-use crate::{prelude::*, IconAsset};
-
-#[derive(Element)]
-pub struct IconButton {
-    icon: IconAsset,
-    color: IconColor,
-    variant: ButtonVariant,
-    state: InteractionState,
-}
-
-pub fn icon_button() -> IconButton {
-    IconButton {
-        icon: IconAsset::default(),
-        color: IconColor::default(),
-        variant: ButtonVariant::default(),
-        state: InteractionState::default(),
-    }
-}
-
-impl IconButton {
-    pub fn new(icon: IconAsset) -> Self {
-        Self {
-            icon,
-            color: IconColor::default(),
-            variant: ButtonVariant::default(),
-            state: InteractionState::default(),
-        }
-    }
-
-    pub fn icon(mut self, icon: IconAsset) -> Self {
-        self.icon = icon;
-        self
-    }
-
-    pub fn color(mut self, color: IconColor) -> Self {
-        self.color = color;
-        self
-    }
-
-    pub fn variant(mut self, variant: ButtonVariant) -> Self {
-        self.variant = variant;
-        self
-    }
-
-    pub fn state(mut self, state: InteractionState) -> Self {
-        self.state = state;
-        self
-    }
-
-    fn render<V: 'static>(&mut self, _: &mut V, cx: &mut ViewContext<V>) -> impl IntoElement<V> {
-        let theme = theme(cx);
-
-        let icon_color = match (self.state, self.color) {
-            (InteractionState::Disabled, _) => IconColor::Disabled,
-            _ => self.color,
-        };
-
-        let mut div = div();
-        if self.variant == ButtonVariant::Filled {
-            div = div.fill(theme.highest.on.default.background);
-        }
-
-        div.w_7()
-            .h_6()
-            .flex()
-            .items_center()
-            .justify_center()
-            .rounded_md()
-            .hover()
-            .fill(theme.highest.base.hovered.background)
-            .active()
-            .fill(theme.highest.base.pressed.background)
-            .child(icon(self.icon).color(icon_color))
-    }
-}