Merge #10872

10872: ide_db: build symbol index from crate def map r=Veykril a=jhgg

fixes #4842, #10764

Is this looking correct? 👀 

- [x] build the symbol index based upon the CrateDefMap for the given crate in `crate_symbols`
   - [x] make it multi threaded again, and figure out how to cache each moduleid's symbol index in salsa.
   - [x] NavigationTarget for names in macros is wrong, need to figure out how to compute a text range in the original file id?
   - [x] cleanup some duped code
   - [x] collect macros from `ItemScope.declared_macros()` into symbol index.
        - [x] store declared macros in `ItemScope` so we can figure out where macros were defined for the index.  
   - [x] do something about `SymbolIndex::for_files` - ideally it should use the new module symbol index stuff. 
       - [x] delete `source_file_to_file_symbols` & co...
           - [x] figure out what to do about `library_symbols` 
           - [x] maybe... speed up the new `library_symbols` - the new impl is probably much slower, and definitely much less parallel. **deciding to do nothing here, we can optimize later if necerssary.** 
   - [x] fix failing test: `navigation_target::tests::test_nav_for_symbol` - notably the crate def map doesn't seem to find declarations inside function. 
       - [x] now a bunch of other tests are failing around auto_import & qualify_path handlers. :(
           - [x] need to assoc items in traits and impls
 

Co-authored-by: Jake Heinz <jh@discordapp.com>

crates/ide/src/lib.rs

@@ -367,8 +367,8 @@ impl Analysis {
     pub fn symbol_search(&self, query: Query) -> Cancellable<Vec<NavigationTarget>> {
         self.with_db(|db| {
             symbol_index::world_symbols(db, query)
-                .into_iter()
-                .map(|s| s.to_nav(db))
+                .into_iter() // xx: should we make this a par iter?
+                .filter_map(|s| s.try_to_nav(db))
                 .collect::<Vec<_>>()
         })
     }