Grammar causes freeze on on long chain of ternary operators

Original issue filed by @nblog in https://github.com/microsoft/vscode/issues/87225
## Details

What editor are you seeing the problem in? (e.g. Atom, Visual Studio Code, etc.)
VS Code
What version of the editor are you using?
1.42 Insiders
What color theme are you using?
not applicable

## Repro
```csharp
CallEvent callEvent = new CallEvent(traceId, (ulong)((callNumber == 0UL) ? ((long)r["CallNumber"]) : ((long)callNumber)), (ulong)((long)r["Peer"]), (int)((long)r["Priority"]), (string)((obj2 == DBNull.Value) ? string.Empty : obj2), (EventFlags)((long)r["EventFlags"]), (ulong)((long)r["RetValue"]), (string)((obj3 == DBNull.Value) ? string.Empty : obj3), (string)((obj4 == DBNull.Value) ? string.Empty : obj4), (HookType)((long)r["HookType"]), (uint)((long)r["ChainDepth"]), (uint)((long)r["Cookie"]), (double)r["Time"], (double)r["GenerationTime"], (int)((long)r["ParamMainIndex"]), (uint)((long)r["Pid"]), (uint)((long)r["Tid"]), (string)((obj5 == DBNull.Value) ? string.Empty : obj5), (string)((obj6 == DBNull.Value) ? string.Empty : obj6), (string)((obj7 == DBNull.Value) ? string.Empty : obj7), (bool)r["Success"], ancestors);
```
This line cause the freeze.

Reproduziere den Freeze in der csharp-tmLanguage-Grammatik mit der bereitgestellten C#-Zeile, die eine lange Kette ternärer Operatoren enthält. Untersuche die Grammatikregeln für verschachtelte ternäre Ausdrücke und verifiziere, dass dieselbe Eingabe nicht mehr zum Freeze führt, während die C#-Syntaxhervorhebung weiterhin funktioniert.

Vom Indexierungsmodell aus dem Issue-Text verfasst.