LibSymbolication+SystemMonitor: Show ELF object in stack

This small patch allows SystemMonitor's Stack tab to show the name of
the ELF object to which the displayed address refers to. This gives a
bit more of contextual information to the viewer.

A better to show this is probably a table, but I'm not that familiar yet
with the GUI framework in general, so I'm keeping things simple.

Userland/Applications/SystemMonitor/ThreadStackWidget.cpp

@@ -79,7 +79,7 @@ void ThreadStackWidget::custom_event(Core::CustomEvent& event)
     StringBuilder builder;
 
     for (auto& symbol : completion_event.symbols()) {
-        builder.appendff("{:p}", symbol.address);
+        builder.appendff("{:p} {:30s}", symbol.address, symbol.object);
         if (!symbol.name.is_empty())
             builder.appendff("  {}", symbol.name);
         builder.append('\n');