processor: Extract HeapGraph parsing into module

.. so it can be disabled at compile time.

Also moves heap_graph_tracker.h/cc into importers/proto, since that's
the only importer that currently uses it.

Bug: 141459049
Change-Id: I500255f7a31e0c936f4180bf0b8cba2e674d9945
diff --git a/Android.bp b/Android.bp
index 9535112..5fe6780 100644
--- a/Android.bp
+++ b/Android.bp
@@ -4623,8 +4623,6 @@
     "src/trace_processor/forwarding_trace_parser.cc",
     "src/trace_processor/ftrace_utils.cc",
     "src/trace_processor/gzip_trace_parser.cc",
-    "src/trace_processor/heap_graph_tracker.cc",
-    "src/trace_processor/heap_graph_walker.cc",
     "src/trace_processor/heap_profile_tracker.cc",
     "src/trace_processor/importers/ftrace/ftrace_descriptors.cc",
     "src/trace_processor/importers/ftrace/ftrace_parser.cc",
@@ -4636,6 +4634,9 @@
     "src/trace_processor/importers/fuchsia/fuchsia_trace_utils.cc",
     "src/trace_processor/importers/proto/android_probes_parser.cc",
     "src/trace_processor/importers/proto/graphics_event_parser.cc",
+    "src/trace_processor/importers/proto/heap_graph_module.cc",
+    "src/trace_processor/importers/proto/heap_graph_tracker.cc",
+    "src/trace_processor/importers/proto/heap_graph_walker.cc",
     "src/trace_processor/importers/proto/proto_trace_parser.cc",
     "src/trace_processor/importers/proto/proto_trace_tokenizer.cc",
     "src/trace_processor/importers/proto/system_probes_parser.cc",
@@ -4681,9 +4682,9 @@
     "src/trace_processor/filtered_row_index_unittest.cc",
     "src/trace_processor/forwarding_trace_parser_unittest.cc",
     "src/trace_processor/ftrace_utils_unittest.cc",
-    "src/trace_processor/heap_graph_walker_unittest.cc",
     "src/trace_processor/heap_profile_tracker_unittest.cc",
     "src/trace_processor/importers/fuchsia/fuchsia_trace_utils_unittest.cc",
+    "src/trace_processor/importers/proto/heap_graph_walker_unittest.cc",
     "src/trace_processor/importers/proto/proto_trace_parser_unittest.cc",
     "src/trace_processor/importers/systrace/systrace_parser_unittest.cc",
     "src/trace_processor/metadata_table_unittest.cc",