Revert "Use Fx* variants of HashMap and HashSet everywhere in Zed" (#7492)

Reverts zed-industries/zed#7481

This would regress performance because we'd be using the standard
library's hash maps everywhere, so reverting for now.

crates/theme/Cargo.toml

@@ -8,7 +8,11 @@ license = "GPL-3.0-or-later"
 [features]
 default = []
 stories = ["dep:itertools", "dep:story"]
-test-support = ["gpui/test-support", "fs/test-support", "settings/test-support"]
+test-support = [
+    "gpui/test-support",
+    "fs/test-support",
+    "settings/test-support"
+]
 
 [lib]
 path = "src/theme.rs"
@@ -16,7 +20,6 @@ doctest = false
 
 [dependencies]
 anyhow.workspace = true
-collections.workspace = true
 color.workspace = true
 derive_more.workspace = true
 fs.workspace = true

crates/theme/src/registry.rs

@@ -1,8 +1,8 @@
+use std::collections::HashMap;
 use std::path::Path;
 use std::sync::Arc;
 
 use anyhow::{anyhow, Context, Result};
-use collections::HashMap;
 use derive_more::{Deref, DerefMut};
 use fs::Fs;
 use futures::StreamExt;
@@ -64,7 +64,7 @@ impl ThemeRegistry {
     pub fn new(assets: Box<dyn AssetSource>) -> Self {
         let registry = Self {
             state: RwLock::new(ThemeRegistryState {
-                themes: HashMap::default(),
+                themes: HashMap::new(),
             }),
             assets,
         };