[clang] Avoid need for SLocEntryLoaded BitVector (PR #67960)

[Vassil Vassilev via cfe-commits]

================
@@ -489,6 +490,8 @@ class SLocEntry {
 
   bool isExpansion() const { return IsExpansion; }
   bool isFile() const { return !isExpansion(); }
+  bool isLoaded() const { return Loaded; }
+  void setLoaded(bool Value) { Loaded = Value; }
----------------
vgvassilev wrote:

```suggestion
  bool isLoaded() const { return IsLoaded; }
  void setLoaded(bool Value) { IsLoaded = Value; }
```

https://github.com/llvm/llvm-project/pull/67960