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/Libraries/LibSymbolication/Symbolication.cpp

@@ -121,6 +121,7 @@ Optional<Symbol> symbolicate(String const& path, FlatPtr address)
     return Symbol {
         .address = address,
         .name = move(symbol),
+        .object = LexicalPath::basename(path),
         .offset = offset,
         .source_positions = move(positions),
     };