Add supports for nested breakdown in 'dmprof cat'.

tools/deep_memory_profiler/sorter.vm-map.json

 {
   "type": "sorter",
   "version": 1,
   "world": "vm",
   "name": "map",
+  "root": true,
   "order": {},
   "rules": [
     {
       "name": "mmap-profiler",
       "backtrace_function": ".*(ProfilerMalloc|MemoryRegionMap::).*",
       "mmap": true,
       "hidden": true
     },
     {
       "name": "mmap-type-profiler",
@@ skipping 23 matching lines @@
       "mmap": false
     },
     {
       "name": "unhooked-other",
       "mapped_pathname": ".*",
       "mmap": false
     },
     {
       "name": "mmap-tcmalloc",
       "backtrace_function": ".*(DoAllocWithArena|SbrkSysAllocator::Alloc|MmapSysAllocator::Alloc|LowLevelAlloc::Alloc|LowLevelAlloc::AllocWithArena).*",
-      "mmap": true,
-      "subworlds": [ "malloc" ]
+      "subs": [
+        [ "malloc", "component" ],
+        [ "malloc", "type" ]
+      ],
+      "mmap": true
     },
     {
       "name": "mmap-v8-heap-newspace",
       "backtrace_function": ".*v8::internal::NewSpace::SetUp.*",
       "mmap": true
     },
     {
       "name": "mmap-v8-heap-coderange",
       "backtrace_function": ".*v8::internal::CodeRange::SetUp.*",
       "mmap": true
@@ skipping 33 matching lines @@
       "backtrace_function": ".*SkTypeface::openStream.*",
       "mmap": true
     },
     {
       "name": "mmap-catch-all",
       "backtrace_function": ".*",
       "mmap": true
     }
   ]
 }