[llvm] [TableGen] Emit `llvm::is_contained` when CheckOpcode accepts a large list (PR #134057)

[Matt Arsenault via llvm-commits]

================
@@ -152,6 +152,18 @@ void PredicateExpander::expandCheckOpcode(raw_ostream &OS,
     return;
   }
 
+  if (Opcodes.size() >= 8) {
+    OS << (shouldNegate() ? "!" : "") << "llvm::is_contained(";
+    ListSeparator Sep;
+    OS << "{";
+    for (const Record *Inst : Opcodes)
+      OS << Sep << Inst->getValueAsString("Namespace")
+         << "::" << Inst->getName();
+    OS << "}";
----------------
arsenm wrote:

```suggestion
    if (shouldNegate())
      OS << '!' << "llvm::is_contained(";
    ListSeparator Sep;
    OS << '{';
    for (const Record *Inst : Opcodes)
      OS << Sep << Inst->getValueAsString("Namespace")
         << "::" << Inst->getName();
    OS << '}';
```

https://github.com/llvm/llvm-project/pull/134057