[release/6.0-preview7] [debugger] Export mono_debugger_agent_unhandled_exception to avoid usage of Debugger.Mono_UnhandledException (#56071)

* Avoid regressing behavior that we had on mono/mono. Xamarin Android team will be able to use mono_debugger_agent_unhandled_exception, and do not use Debugger.Mono_UnhandledException(as it does not exist on net6).

* Exporting headers

* Fixing implementation.

Author: thaystg

src/mono/mono/metadata/debug-helpers.h

@@ -48,6 +48,9 @@ MONO_API char*           mono_method_get_reflection_name (MonoMethod *method);
 
 MONO_API char*           mono_field_full_name (MonoClassField *field);
 
+MONO_API MONO_RT_EXTERNAL_ONLY void
+mono_debugger_agent_unhandled_exception (MonoException *e);
+
 MONO_END_DECLS
 
 #endif /* __MONO_DEBUG_HELPERS_H__ */

src/mono/mono/mini/debugger-agent-external.c

@@ -5,6 +5,7 @@
 #include <glib.h>
 #include <mono/metadata/components.h>
 #include "debugger-agent-external.h"
+#include <mono/metadata/external-only.h>
 
 #ifndef DISABLE_SDB
 
@@ -59,4 +60,12 @@ mono_debugger_agent_get_sdb_options (void)
 {
 	return sdb_options;
 }
+
+void
+mono_debugger_agent_unhandled_exception (MonoException *e)
+{
+	MONO_ENTER_GC_UNSAFE;
+	MONO_EXTERNAL_ONLY_VOID (mono_component_debugger ()->unhandled_exception (e));
+	MONO_EXIT_GC_UNSAFE;
+}
 #endif /* DISABLE_SDB */

src/mono/mono/mini/mini-runtime.c

@@ -4607,11 +4607,6 @@ register_icalls (void)
 	mono_add_internal_call_internal ("Mono.Runtime::mono_runtime_install_handlers",
 				mono_runtime_install_handlers);
 
-#if defined(HOST_ANDROID) || defined(TARGET_ANDROID)
-	mono_add_internal_call_internal ("System.Diagnostics.Debugger::Mono_UnhandledException_internal",
-							mono_component_debugger ()->unhandled_exception);
-#endif
-
 	/*
 	 * It's important that we pass `TRUE` as the last argument here, as
 	 * it causes the JIT to omit a wrapper for these icalls. If the JIT