[red-knot] Improve symbol-lookup tracing (#14907)

## Summary

When debugging, I frequently want to know which symbols are being looked
up. `symbol_by_id` adds tracing information, but it only shows the
`ScopedSymbolId`. Since `symbol_by_id` is only called from `symbol`, it
seems reasonable to move the tracing call one level up from
`symbol_by_id` to `symbol`, where we can also show the name of the
symbol.

**Before**:

```
6      └─┐red_knot_python_semantic::types::infer::infer_expression_types{expression=Id(60de), file=/home/shark/tomllib_modified/_parser.py}
6        └─┐red_knot_python_semantic::types::symbol_by_id{symbol=ScopedSymbolId(33)}
6        ┌─┘
6        └─┐red_knot_python_semantic::types::symbol_by_id{symbol=ScopedSymbolId(123)}
6        ┌─┘
6        └─┐red_knot_python_semantic::types::symbol_by_id{symbol=ScopedSymbolId(54)}
6        ┌─┘
6        └─┐red_knot_python_semantic::types::symbol_by_id{symbol=ScopedSymbolId(122)}
6        ┌─┘
6        └─┐red_knot_python_semantic::types::symbol_by_id{symbol=ScopedSymbolId(165)}
6        ┌─┘
6      ┌─┘
6      └─┐red_knot_python_semantic::types::symbol_by_id{symbol=ScopedSymbolId(32)}
6      ┌─┘
6      └─┐red_knot_python_semantic::types::symbol_by_id{symbol=ScopedSymbolId(232)}
6      ┌─┘
6    ┌─┘
6  ┌─┘
6┌─┘
```

**After**:

```
5      └─┐red_knot_python_semantic::types::infer::infer_expression_types{expression=Id(60de), file=/home/shark/tomllib_modified/_parser.py}
5        └─┐red_knot_python_semantic::types::symbol{name="dict"}
5        ┌─┘
5        └─┐red_knot_python_semantic::types::symbol{name="dict"}
5        ┌─┘
5        └─┐red_knot_python_semantic::types::symbol{name="list"}
5        ┌─┘
5        └─┐red_knot_python_semantic::types::symbol{name="list"}
5        ┌─┘
5        └─┐red_knot_python_semantic::types::symbol{name="isinstance"}
5        ┌─┘
5        └─┐red_knot_python_semantic::types::symbol{name="isinstance"}
5        ┌─┘
5      ┌─┘
5      └─┐red_knot_python_semantic::types::symbol{name="ValueError"}
5      ┌─┘
5      └─┐red_knot_python_semantic::types::symbol{name="ValueError"}
5      ┌─┘
5    ┌─┘
5  ┌─┘
5┌─┘
```

## Test Plan

```
cargo run --bin red_knot -- --current-directory path/to/tomllib -vvv
```

crates/red_knot_python_semantic/src/types.rs

@@ -74,10 +74,13 @@ pub fn check_types(db: &dyn Db, file: File) -> TypeCheckDiagnostics {
 }
 
 /// Infer the public type of a symbol (its type as seen from outside its scope).
-#[salsa::tracked]
-fn symbol_by_id<'db>(db: &'db dyn Db, scope: ScopeId<'db>, symbol: ScopedSymbolId) -> Symbol<'db> {
-    let _span = tracing::trace_span!("symbol_by_id", ?symbol).entered();
-
+fn symbol<'db>(db: &'db dyn Db, scope: ScopeId<'db>, name: &str) -> Symbol<'db> {
+    #[salsa::tracked]
+    fn symbol_by_id<'db>(
+        db: &'db dyn Db,
+        scope: ScopeId<'db>,
+        symbol: ScopedSymbolId,
+    ) -> Symbol<'db> {
         let use_def = use_def_map(db, scope);
 
         // If the symbol is declared, the public type is based on declarations; otherwise, it's based
@@ -136,10 +139,10 @@ fn symbol_by_id<'db>(db: &'db dyn Db, scope: ScopeId<'db>, symbol: ScopedSymbolI
         // If we import from this module, we will currently report `x` as a definitely-bound symbol
         // (even though it has no bindings at all!) but report `y` as possibly-unbound (even though
         // every path has either a binding or a declaration for it.)
-}
+    }
+
+    let _span = tracing::trace_span!("symbol", ?name).entered();
 
-/// Shorthand for `symbol_by_id` that takes a symbol name instead of an ID.
-fn symbol<'db>(db: &'db dyn Db, scope: ScopeId<'db>, name: &str) -> Symbol<'db> {
     // We don't need to check for `typing_extensions` here, because `typing_extensions.TYPE_CHECKING`
     // is just a re-export of `typing.TYPE_CHECKING`.
     if name == "TYPE_CHECKING"