LibELF+LibCoreDump: Add a ProcessInfo notes entry

This is a new NotesEntry type which contains information related to the
coredump's process:

- PID
- executable path

Having these in the coredump explicitly avoids having to parse them from
the coredump filename and backtrace, respectively.

Libraries/LibCoreDump/Reader.h

@@ -44,6 +44,8 @@ public:
 
     Reader(OwnPtr<MappedFile>&&);
 
+    const ELF::Core::ProcessInfo& process_info() const;
+
     template<typename Func>
     void for_each_memory_region_info(Func func) const;