Profiler: Add source code view

This adds a new view mode to profiler which displays source lines and
samples that occured at those lines. This view can be opened via the
menu or by pressing CTRL-S.

It does this by mapping file names from DWARF to "/usr/src/serenity/..."
i.e. source code should be copied to /usr/src/serenity/Userland and
/usr/src/serenity/Kernel to be visible in this mode.

Currently *all* files contributing to the selected function are loaded
completely which could be a lot of data when dealing with lots of
inlined code.

Userland/DevTools/Profiler/Profile.cpp

@@ -8,6 +8,7 @@
 #include "DisassemblyModel.h"
 #include "ProfileModel.h"
 #include "SamplesModel.h"
+#include "SourceModel.h"
 #include <AK/HashTable.h>
 #include <AK/LexicalPath.h>
 #include <AK/NonnullOwnPtrVector.h>
@@ -554,6 +555,23 @@ GUI::Model* Profile::disassembly_model()
     return m_disassembly_model;
 }
 
+void Profile::set_source_index(GUI::ModelIndex const& index)
+{
+    if (m_source_index == index)
+        return;
+    m_source_index = index;
+    auto* node = static_cast<ProfileNode*>(index.internal_data());
+    if (!node)
+        m_source_model = nullptr;
+    else
+        m_source_model = SourceModel::create(*this, *node);
+}
+
+GUI::Model* Profile::source_model()
+{
+    return m_source_model;
+}
+
 ProfileNode::ProfileNode(Process const& process)
     : m_root(true)
     , m_process(process)