"track-app" service showing debuggable/profileable apps

Add a "track-app" service in adbd. For every debuggable or
profileable-from-shell process, ART sends related info to
adbd and adbd surfaces the info through the "track-app"
service.

The output format of "track-app" is a line summarizing
the number of reported processes, followed by a protobuf
message in human readable form. For example,

Process count: 2
process {
  pid: 3307
  profileable: true
  architecture: "arm64"
}
process {
  pid: 3341
  debuggable: true
  profileable: true
  architecture: "arm64"
}

Bug: 149050485
Test: manually unplugged/replugged, "adb track-app",
      "adb track-jdwp"
Change-Id: Id1f1a920e1afc148c7e4d2add790baab796178e1
diff --git a/adb/daemon/services.cpp b/adb/daemon/services.cpp
index 6bbf66e..a9d1fe8 100644
--- a/adb/daemon/services.cpp
+++ b/adb/daemon/services.cpp
@@ -241,6 +241,8 @@
         return create_jdwp_service_socket();
     } else if (name == "track-jdwp") {
         return create_jdwp_tracker_service_socket();
+    } else if (name == "track-app") {
+        return create_app_tracker_service_socket();
     } else if (android::base::ConsumePrefix(&name, "sink:")) {
         uint64_t byte_count = 0;
         if (!ParseUint(&byte_count, name)) {