Bring back in-rust-tree feature to ide

Author: lnicola

src/tools/rust-analyzer/crates/ide/Cargo.toml

@@ -51,5 +51,8 @@ expect-test = "1.4.0"
 test-utils.workspace = true
 test-fixture.workspace = true
 
+[features]
+in-rust-tree = []
+
 [lints]
 workspace = true