[lldb] Consult Language plugin in GetDisplayDemangledName (llvm#90294)

Give language plugins the opportunity to provide a language specific
display name.

This will be used in a follow up commit. The purpose of this change is
to ultimately display breakpoint locations with a more human friendly
demangling of Swift symbols.

(cherry picked from commit b52160d)

Author: kastiglione

lldb/include/lldb/Target/Language.h

@@ -270,6 +270,10 @@ class Language : public PluginInterface {
     return mangled.GetMangledName();
   }
 
+  virtual ConstString GetDisplayDemangledName(Mangled mangled) const {
+    return mangled.GetDemangledName();
+  }
+
   virtual void GetExceptionResolverDescription(bool catch_on, bool throw_on,
                                                Stream &s);
 

lldb/source/Core/Mangled.cpp

@@ -337,6 +337,8 @@ ConstString Mangled::GetDisplayDemangledName(
         m_mangled.GetStringRef(), SwiftLanguageRuntime::eSimplified, sc));
 #endif // LLDB_ENABLE_SWIFT
 // END SWIFT
+  if (Language *lang = Language::FindPlugin(GuessLanguage()))
+    return lang->GetDisplayDemangledName(*this);
   return GetDemangledName();
 }