Restructure find_path into a separate functions for modules and non-module items

Also renames `prefer_core` imports config to `prefer_no_std` and changes the behavior of no_std path searching by preferring `core` paths `over` alloc

crates/ide-diagnostics/src/lib.rs

@@ -150,7 +150,7 @@ pub struct DiagnosticsConfig {
     pub expr_fill_default: ExprFillDefaultMode,
     // FIXME: We may want to include a whole `AssistConfig` here
     pub insert_use: InsertUseConfig,
-    pub prefer_core: bool,
+    pub prefer_no_std: bool,
 }
 
 impl DiagnosticsConfig {
@@ -171,7 +171,7 @@ impl DiagnosticsConfig {
                 group: false,
                 skip_glob_imports: false,
             },
-            prefer_core: false,
+            prefer_no_std: false,
         }
     }
 }