Kernel: Generate a coredump file when a process crashes

When a process crashes, we generate a coredump file and write it in
/tmp/coredumps/.

The coredump file is an ELF file of type ET_CORE.
It contains a segment for every userspace memory region of the process,
and an additional PT_NOTE segment that contains the registers state for
each thread, and a additional data about memory regions
(e.g their name).

Kernel/Thread.cpp

@@ -734,6 +734,7 @@ DispatchSignalResult Thread::dispatch_signal(u8 signal)
             set_state(Stopped, signal);
             return DispatchSignalResult::Yield;
         case DefaultSignalAction::DumpCore:
+            process.set_dump_core(true);
             process.for_each_thread([](auto& thread) {
                 thread.set_dump_backtrace_on_finalization();
                 return IterationDecision::Continue;