boot: implement --unhandled-exception=stalldebug (#1690)

Using this option will stall the crashed thread until the debugger
attaches, so that the newly attached debugger can be handed over the
exception, enabling breaking at correct stack location.

`--no-exception-handlers` injector option controlled whether Dalamud
Crash Handler would intercept exceptions before. Those are now either
`default` or `none` option for `--unhandled-exception`.

Dalamud.Common/DalamudStartInfo.cs

@@ -145,7 +145,7 @@ public record DalamudStartInfo
     public bool CrashHandlerShow { get; set; }
 
     /// <summary>
-    /// Gets or sets a value indicating whether to disable all kinds of global exception handlers.
+    /// Gets or sets a value indicating how to deal with unhandled exceptions.
     /// </summary>
-    public bool NoExceptionHandlers { get; set; }
+    public UnhandledExceptionHandlingMode UnhandledException { get; set; }
 }

Dalamud.Common/UnhandledExceptionHandlingMode.cs

@@ -0,0 +1,16 @@
+namespace Dalamud.Common;
+
+/// <summary>Enum describing what to do on unhandled exceptions.</summary>
+public enum UnhandledExceptionHandlingMode
+{
+    /// <summary>Always show Dalamud Crash Handler on crash, except for some exceptions.</summary>
+    /// <remarks>See `vectored_exception_handler` in `veh.cpp`.</remarks>
+    Default,
+
+    /// <summary>Waits for debugger if none is attached, and pass the exception to the next handler.</summary>
+    /// <remarks>See `exception_handler` in `veh.cpp`.</remarks>
+    StallDebug,
+
+    /// <summary>Do not register an exception handler.</summary>
+    None,
+}