Kernel+SystemMonitor: Add fault counters

This patch adds three separate per-process fault counters:

- Inode faults

    An inode fault happens when we've memory-mapped a file from disk
    and we end up having to load 1 page (4KB) of the file into memory.

- Zero faults

    Memory returned by mmap() is lazily zeroed out. Every time we have
    to zero out 1 page, we count a zero fault.

- CoW faults

    VM objects can be shared by multiple mappings that make their own
    unique copy iff they want to modify it. The typical reason here is
    memory shared between a parent and child process.

Kernel/FileSystem/ProcFS.cpp

@@ -685,6 +685,9 @@ Optional<KBuffer> procfs$all(InodeIdentifier)
         process_object.add("ticks", process.main_thread().ticks());
         process_object.add("priority", to_string(process.priority()));
         process_object.add("syscall_count", process.syscall_count());
+        process_object.add("inode_faults", process.inode_faults());
+        process_object.add("zero_faults", process.zero_faults());
+        process_object.add("cow_faults", process.cow_faults());
         process_object.add("icon_id", process.icon_id());
     };
     build_process(*Scheduler::colonel());