Ensure font features are applied to styled text (#44219)

- Replace `gpui::styled::Styled.font_family()` calls with
`gpui::styled::Styled.font()` when laying out inline diagnostics and
inline blame, to ensure that the font's features are also used, and
not just the font feature.
- Update both `editor::hover_popover::hover_markdown_style` and
`editor::hover_popover::diagnostics_markdown_style` to ensure that
both the UI and Buffer font features are used in both markdown and
diagnostics popover.

Closes #44209 

Release Notes:

- Fixed font feature application for inline git blame, inline
diagnostics, markdown popovers and diagnostics popovers

crates/git_ui/src/blame_ui.rs

@@ -148,7 +148,7 @@ impl BlameRenderer for GitBlameRenderer {
             h_flex()
                 .id("inline-blame")
                 .w_full()
-                .font_family(style.font().family)
+                .font(style.font())
                 .text_color(cx.theme().status().hint)
                 .line_height(style.line_height)
                 .child(Icon::new(IconName::FileGit).color(Color::Hint))