[clang] [CIR] Upstream get_bitfield operation to load bit-field members from structs (PR #145971)

[Andy Kaylor via cfe-commits]

================
@@ -375,4 +375,42 @@ def CIR_VisibilityAttr : CIR_EnumAttr<CIR_VisibilityKind, "visibility"> {
   }];
 }
 
+//===----------------------------------------------------------------------===//
+// BitfieldInfoAttr
+//===----------------------------------------------------------------------===//
+
+def BitfieldInfoAttr : CIR_Attr<"BitfieldInfo", "bitfield_info"> {
+  let summary = "Represents a bit field info";
+  let description = [{
+    Holds the next information about bitfields: name, storage type, a bitfield
+    size and position in the storage, if the bitfield is signed or not.
----------------
andykaylor wrote:

```suggestion
    Holds the following information about bitfields: name, storage type, size
    and position in the storage, and signedness.
```

https://github.com/llvm/llvm-project/pull/145971