Rename ThemeVariant to Theme (#3252)

This PR renames the `ThemeVariant` type to `Theme`.

This better reflects its purpose, as well as matches the same name as we
had before, which should make porting crates slightly easier.

Release Notes:

- N/A

crates/theme_importer/src/theme_printer.rs

@@ -3,7 +3,7 @@ use std::fmt::{self, Debug};
 use gpui::{Hsla, Rgba};
 use theme::{
     Appearance, GitStatusColors, PlayerColor, PlayerColors, StatusColors, SyntaxTheme,
-    SystemColors, ThemeColors, ThemeFamily, ThemeStyles, ThemeVariant,
+    SystemColors, Theme, ThemeColors, ThemeFamily, ThemeStyles,
 };
 
 struct RawSyntaxPrinter<'a>(&'a str);
@@ -68,7 +68,7 @@ impl Debug for ThemeFamilyPrinter {
     }
 }
 
-pub struct ThemeVariantPrinter<'a>(&'a ThemeVariant);
+pub struct ThemeVariantPrinter<'a>(&'a Theme);
 
 impl<'a> Debug for ThemeVariantPrinter<'a> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

crates/theme_importer/src/vscode.rs

@@ -2,8 +2,8 @@ use anyhow::Result;
 use gpui::{Hsla, Refineable, Rgba};
 use serde::Deserialize;
 use theme::{
-    Appearance, GitStatusColors, PlayerColors, StatusColors, SyntaxTheme, SystemColors,
-    ThemeColors, ThemeColorsRefinement, ThemeStyles, ThemeVariant,
+    Appearance, GitStatusColors, PlayerColors, StatusColors, SyntaxTheme, SystemColors, Theme,
+    ThemeColors, ThemeColorsRefinement, ThemeStyles,
 };
 
 use crate::util::Traverse;
@@ -433,7 +433,7 @@ impl VsCodeThemeConverter {
         }
     }
 
-    pub fn convert(self) -> Result<ThemeVariant> {
+    pub fn convert(self) -> Result<Theme> {
         let appearance = self.theme_metadata.appearance.into();
 
         let mut theme_colors = match appearance {
@@ -569,7 +569,7 @@ impl VsCodeThemeConverter {
 
         theme_colors.refine(&theme_colors_refinements);
 
-        Ok(ThemeVariant {
+        Ok(Theme {
             id: uuid::Uuid::new_v4().to_string(),
             name: self.theme_metadata.name.into(),
             appearance,