Auto merge of #17973 - Veykril:proc-macro-curr-dir, r=Veykril

Expand proc-macros in workspace root, not package root

Should fix https://github.com/rust-lang/rust-analyzer/issues/17748. The approach is generally not perfect though as rust-project.json projects don't benefit from this (still, nothing changes in that regard)

crates/project-model/src/cargo_workspace.rs

@@ -241,6 +241,10 @@ impl TargetKind {
     pub fn is_executable(self) -> bool {
         matches!(self, TargetKind::Bin | TargetKind::Example)
     }
+
+    pub fn is_proc_macro(self) -> bool {
+        matches!(self, TargetKind::Lib { is_proc_macro: true })
+    }
 }
 
 // Deserialize helper for the cargo metadata