Revise and clean up some icons (#35582)

This is really just a small beginning, as there are many other icons to
be revised and cleaned up. Our current set is a bit of a mess in terms
of dimension, spacing, stroke width, and terminology. I'm sure there are
more non-used icons I'm not covering here, too. We'll hopefully tackle
it all soon leading up to 1.0.

Closes https://github.com/zed-industries/zed/issues/35576

Release Notes:

- N/A

crates/ui/src/components/stories/icon_button.rs

@@ -77,7 +77,7 @@ impl Render for IconButtonStory {
 
         let with_tooltip_button = StoryItem::new(
             "With `tooltip`",
-            IconButton::new("with_tooltip_button", IconName::MessageBubbles)
+            IconButton::new("with_tooltip_button", IconName::Chat)
                 .tooltip(Tooltip::text("Open messages")),
         )
         .description("Displays an icon button that has a tooltip when hovered.")