zlog: Replace usages of env_logger in tests with zlog (#31436)

Also fixes:
https://github.com/zed-industries/zed/pull/31400#issuecomment-2908165249

Release Notes:

- N/A *or* Added/Fixed/Improved ...

crates/tab_switcher/Cargo.toml

@@ -32,9 +32,9 @@ workspace-hack.workspace = true
 [dev-dependencies]
 anyhow.workspace = true
 ctor.workspace = true
-env_logger.workspace = true
 gpui = { workspace = true, features = ["test-support"] }
 language = { workspace = true, features = ["test-support"] }
 serde_json.workspace = true
 theme = { workspace = true, features = ["test-support"] }
 workspace = { workspace = true, features = ["test-support"] }
+zlog.workspace = true

crates/tab_switcher/src/tab_switcher_tests.rs

@@ -10,9 +10,7 @@ use workspace::{AppState, Workspace};
 
 #[ctor::ctor]
 fn init_logger() {
-    if std::env::var("RUST_LOG").is_ok() {
-        env_logger::init();
-    }
+    zlog::init_test();
 }
 
 #[gpui::test]