[clang] [CIR] Add support for the IdiomRecognizer pass (PR #208854)

[Erich Keane via cfe-commits]

================
@@ -1296,11 +1296,52 @@ def CIR_CXXAssignAttr : CIR_Attr<"CXXAssign", "cxx_assign"> {
 // FuncInfoAttr
 //===----------------------------------------------------------------------===//
 
+// The standard library entities the identity tag can name. Each entry
+// pairs with one raised operation in CIRStdOps.td.
+def CIR_KnownFuncKind : CIR_I32EnumAttr<"KnownFuncKind",
+    "known standard library entity", [
+  I32EnumAttrCase<"StdFind", 1, "std_find">,
----------------
erichkeane wrote:

```suggestion
  I32EnumAttrCase<"StdFind", 1, "std::find">,
```

Silly question: CAN we do this? 

https://github.com/llvm/llvm-project/pull/208854